# LATS1 Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- LATS1 is a central serine/threonine kinase in the Hippo pathway, acting as a tumor suppressor by phosphorylating and inhibiting YAP1/TAZ, thereby restricting pro-proliferative gene transcription.
- Recurrent somatic mutations in LATS1, such as R684Q in the kinase hinge and S1091F in the hydrophobic motif, are frequently observed in various cancers and lead to loss of kinase activity or impaired activation.
- LATS1 plays critical roles beyond the Hippo pathway, including regulating mitotic progression by inhibiting Aurora A kinase and contributing to genome stability through its involvement in DNA damage response and homologous recombination repair.
- Viral oncoproteins from HPV (E6) and HBV (HBx), as well as SARS-CoV-2 protease NSP5, can directly target LATS1 for degradation or inactivation, contributing to oncogenesis and disease pathology.
- Therapeutic strategies involve either reactivating LATS1 in tumors where it is lost (e.g., using statins or dasatinib) or inhibiting LATS1/2 to promote YAP1-driven tissue regeneration (e.g., via MST1/2 inhibitors like XMU-MP-1).

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## Executive Summary & Key Metadata

The *LATS1* (Large Tumor Suppressor Kinase 1) gene encodes a serine/threonine protein kinase that functions as a central node in the Hippo signaling pathway, a conserved growth-regulatory cascade that controls organ size, cell proliferation, and apoptosis. LATS1, along with its paralog LATS2, phosphorylates and inhibits the transcriptional co-activators YAP1 (Yes-associated protein 1) and WWTR1 (TAZ), thereby restricting their nuclear translocation and pro-proliferative transcriptional programs. Beyond its canonical Hippo function, LATS1 participates in mitotic progression, cytoskeletal dynamics, DNA damage response, and immune modulation. Loss-of-function mutations, epigenetic silencing, or dysregulated expression of LATS1 are recurrent events across a broad spectrum of human malignancies, including breast, lung, colorectal, liver, and ovarian cancers. This manual provides a comprehensive, biophysically grounded reference covering the genomic architecture, structural biology, signaling networks, pathogenic mutations, viral interactions, pharmacogenomic landscape, and bioinformatic resources for LATS1.

| **Attribute** | **Value** |
|---|---|
| HGNC Symbol | LATS1 |
| UniProt Accession | O95835 |
| Representative PDB ID | 5ZBR (kinase domain) |
| Chromosomal Locus | 6q25.1 |
| Primary Molecular Function | Serine/threonine kinase; Hippo pathway core kinase; YAP1/TAZ phosphorylation |
| Disease & Pathology Associations | Breast cancer, non-small cell lung cancer, colorectal cancer, hepatocellular carcinoma, ovarian cancer, glioblastoma, sarcomas |
| Gene Type | Protein-coding |
| Exon Count | 8 exons (canonical transcript) |
| Protein Length | 1,130 amino acids (isoform 1) |
| Molecular Weight | ~126.9 kDa |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Localization and Coordinates

The *LATS1* gene is located on the long (q) arm of chromosome 6 at cytogenetic band 6q25.1. In the GRCh38/hg38 human reference genome assembly, *LATS1* spans approximately 113 kilobases (kb) of genomic DNA, from position 149,658,153 to 149,771,832 (reverse strand). The gene is oriented on the minus strand of chromosome 6, meaning transcription proceeds in the 3′→5′ direction relative to the chromosomal coordinate system.

The 6q25.1 region is a well-established tumor suppressor locus. Frequent loss of heterozygosity (LOH) at 6q24–q25 has been documented in multiple cancer types, including breast, ovarian, and hepatocellular carcinomas, suggesting that *LATS1* resides within a critical minimal deleted region. The gene's proximity to other tumor suppressors, such as *ESR1* (estrogen receptor alpha, located ~1.5 Mb centromeric) and *IGF2R* (insulin-like growth factor 2 receptor, ~3 Mb telomeric), complicates the attribution of tumor suppressive effects solely to LATS1 loss in LOH studies, but functional studies have unequivocally established LATS1 as a bona fide suppressor.

### 1.2 Promoter Architecture and Regulatory Elements

The *LATS1* promoter region lacks a canonical TATA box but contains a high-density CpG island spanning approximately 1.2 kb upstream of the transcription start site (TSS) and extending into exon 1. This CpG island is a target for epigenetic silencing: hypermethylation of the *LATS1* promoter has been reported in breast cancer, gastric cancer, and acute lymphoblastic leukemia, correlating with reduced mRNA and protein expression.

Multiple transcription factor binding sites have been experimentally validated or computationally predicted within the proximal promoter (−500 bp to +100 bp relative to TSS):

- **p53 (TP53)**: The *LATS1* promoter contains a functional p53 response element, and LATS1 is transcriptionally upregulated in response to DNA damage in a p53-dependent manner. This establishes a feed-forward loop wherein p53 induces LATS1, which in turn phosphorylates and inhibits YAP1, preventing YAP1-mediated suppression of p53.
- **E2F family members**: E2F1 and E2F4 bind the *LATS1* promoter and regulate its cell-cycle-dependent expression. LATS1 mRNA levels peak during the G2/M phase, consistent with E2F-mediated transcriptional control.
- **FOXO3**: Forkhead box O3 (FOXO3) transcriptionally activates *LATS1* under conditions of oxidative stress, linking metabolic stress signaling to Hippo pathway activation.
- **TEAD4**: In a negative feedback loop, TEAD4 (a YAP1/TAZ binding partner) can directly repress *LATS1* transcription, creating an autoregulatory circuit where high YAP/TAZ activity suppresses the kinase that would otherwise inhibit them.

### 1.3 Enhancer Elements and Chromatin Architecture

Chromatin conformation capture studies (Hi-C) in human mammary epithelial cells have identified several putative enhancer elements within intron 1 and intron 3 of *LATS1* that physically interact with the promoter via chromatin looping. These enhancers are enriched for H3K27ac (active enhancer mark) and bind the transcription factors GATA3 and FOXA1 in luminal breast epithelial cells. The intronic enhancer in intron 3 is particularly notable because it harbors a common single-nucleotide polymorphism (rs3737226) that has been associated with altered *LATS1* expression in population studies, although the functional consequence of this variant remains incompletely characterized.

### 1.4 Alternative Splicing and Isoform Diversity

The canonical *LATS1* transcript (NM_004690.4) comprises 8 exons and encodes a 1,130-amino-acid protein. However, multiple alternative splicing events generate isoform diversity:

- **Isoform 2 (NM_001270519.2)**: Retains a portion of intron 6, introducing a premature stop codon. This isoform encodes a truncated protein of 703 amino acids that lacks the entire C-terminal kinase domain. This isoform is predicted to undergo nonsense-mediated decay (NMD) under normal conditions but may be stabilized in certain cancer contexts, potentially acting as a dominant-negative regulator.
- **Isoform 3 (NR_073132.2)**: A non-coding RNA isoform that retains intron 1 and is subject to NMD. Its physiological relevance is unclear, but its expression is detectable in testis and placenta.
- **Exon 4 skipping**: A minor isoform lacking exon 4 (encoding residues 247–310 within the N-terminal regulatory region) has been detected in RNA-seq datasets from brain tissue. This deletion removes a portion of the protein's N-terminal domain that mediates interaction with MOB1, potentially altering kinase activation dynamics.

The regulation of alternative splicing of *LATS1* is mediated by the splicing factors SRSF1 and PTBP1, which bind to exonic splicing enhancers and silencers, respectively. Dysregulation of these splicing factors in cancer may contribute to aberrant LATS1 isoform expression.

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Primary Structure and Domain Organization

The LATS1 protein (UniProt O95835) is a 1,130-amino-acid polypeptide organized into distinct functional domains from the N-terminus to the C-terminus:

| **Domain** | **Residues (approx.)** | **Function** |
|---|---|---|
| N-terminal regulatory region | 1–450 | Mediates protein-protein interactions; contains ubiquitin-associated (UBA)-like fold; autoinhibitory |
| Serine-rich region | 450–600 | Contains phosphorylation sites for CDK1 and Aurora A; regulates mitotic localization |
| MOB1-binding domain | 600–700 | Binds MOB1A/MOB1B co-activators |
| Catalytic kinase domain | 704–990 | Serine/threonine kinase; contains ATP-binding pocket and activation loop |
| Hydrophobic motif | 1079–1085 | Contains phosphorylation site (S1091) for MST1/MST2 |
| C-terminal tail | 990–1130 | Contains PPxY motifs for WW domain interactions; nuclear localization signal |

### 2.2 N-Terminal Regulatory Region

The N-terminal region (residues 1–450) of LATS1 is largely intrinsically disordered but contains a structured UBA-like domain (residues 120–200). Unlike canonical UBA domains that bind ubiquitin, the LATS1 UBA-like domain has evolved to mediate homodimerization and heterodimerization with LATS2. This dimerization is required for autophosphorylation and full kinase activation. Structural studies using small-angle X-ray scattering (SAXS) indicate that the N-terminal region adopts an extended, flexible conformation in solution, allowing it to sample multiple conformations for interaction with binding partners.

The N-terminus also contains a nuclear export signal (NES) at residues 90–100 and a nuclear localization signal (NLS) at residues 410–430. The balance between these signals determines the nucleocytoplasmic shuttling of LATS1, which is critical for its function in both the cytoplasm (Hippo signaling) and nucleus (mitotic regulation).

### 2.3 Catalytic Kinase Domain

The kinase domain (residues 704–990) adopts the canonical bilobed fold of eukaryotic serine/threonine kinases:

- **N-lobe** (residues 704–810): Comprises a five-stranded β-sheet and the αC-helix. The ATP-binding pocket is formed at the interface between the N-lobe and C-lobe, with the hinge region (residues 810–820) connecting the two lobes.
- **C-lobe** (residues 821–990): Contains the catalytic loop (HRD motif, residues 850–852), the DFG motif (residues 880–882), and the activation loop (residues 890–920).

The activation loop of LATS1 contains two critical phosphorylation sites: **T909** and **T913**. Phosphorylation of these residues by MST1/MST2 (in complex with MOB1) induces a conformational change that repositions the activation loop, allowing substrate access to the catalytic cleft. The kinase domain also contains a conserved **APE motif** (residues 930–932) that stabilizes the active conformation.

The ATP-binding pocket of LATS1 is relatively large and hydrophobic compared to other AGC family kinases, a feature that has implications for inhibitor selectivity. The gatekeeper residue is **M841** (methionine), which is larger than the threonine gatekeeper found in many other kinases, potentially limiting access to certain type II inhibitors.

### 2.4 Hydrophobic Motif and C-Terminal Tail

The hydrophobic motif (residues 1079–1085) contains the critical phosphorylation site **S1091**. Phosphorylation of S1091 by MST1/MST2 creates a docking site for the phospho-binding protein 14-3-3, which stabilizes LATS1 in an active conformation. This motif is conserved across AGC kinase family members and is essential for maximal kinase activity.

The C-terminal tail (residues 990–1130) contains two **PPxY motifs** (residues 1005–1008 and 1045–1048) that mediate interactions with WW domain-containing proteins, including YAP1 and TAZ. These interactions are thought to facilitate substrate presentation and processive phosphorylation. The C-terminus also contains a leucine-rich nuclear export signal that regulates the cytoplasmic retention of LATS1.

### 2.5 Structural Insights from Cryo-EM and X-Ray Crystallography

The kinase domain of LATS1 has been solved by X-ray crystallography (PDB: 5ZBR) at 2.8 Å resolution in its inactive conformation. The structure reveals an autoinhibited state in which the activation loop adopts a conformation that blocks substrate binding. A notable feature is an extended β-hairpin insertion in the C-lobe (residues 940–960) that is unique to LATS kinases and is not present in other AGC family members. This insertion creates a hydrophobic groove that may serve as a docking site for substrates or regulatory proteins.

More recently, cryo-electron microscopy (cryo-EM) studies of the MST1-MOB1-LATS1 complex have provided insights into the activation mechanism. These structures show that MOB1 binds to a conserved surface on the N-terminal lobe of the LATS1 kinase domain, inducing a conformational change that promotes MST1-mediated phosphorylation of the activation loop. The complex assembles as a heterotetramer (MST1:MOB1:LATS1:LATS1), with the two LATS1 molecules dimerizing via their N-terminal UBA-like domains.

> **Interactive 3D Protein Visualizer: Load LATS1 (PDB: 5ZBR)**
> [Interactive 3D Protein Visualizer: Load LATS1 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=O95835)
> This visualizer displays the LATS1 kinase domain (residues 704–990) with color-coded secondary structure elements. Key features to explore: the ATP-binding pocket (highlighted in orange), the activation loop (residues 890–920, highlighted in red), and the unique C-lobe β-hairpin insertion (residues 940–960, highlighted in blue). Toggle between cartoon and surface representations to examine the electrostatic potential of the substrate-binding groove.

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 The Hippo Signaling Pathway: Core Cascade

LATS1 is the central kinase of the mammalian Hippo pathway, a signaling cascade that integrates diverse upstream inputs—including cell-cell contact, mechanical cues, GPCR signaling, and metabolic status—to regulate cell proliferation and apoptosis. The core cascade operates as follows:

1. **Upstream activation**: The MST1/MST2 kinases (mammalian Ste20-like kinases) are activated by phosphorylation at their activation loops. This activation is promoted by the scaffolding proteins SAV1 (Salvador homolog 1) and RASSF1A, which recruit MST1/2 to membranes and facilitate autophosphorylation.

2. **MOB1 phosphorylation**: Activated MST1/2 phosphorylate the co-activator proteins MOB1A and MOB1B at T12 and T35, respectively. Phosphorylated MOB1 binds to LATS1/2 and recruits them to the MST1/2-SAV1 complex.

3. **LATS1 activation**: MST1/2 phosphorylate LATS1 at two sites: the hydrophobic motif (S1091) and the activation loop (T909/T913). MOB1 binding to LATS1 induces a conformational change that exposes these sites to MST1/2. Full activation requires autophosphorylation of additional sites within the kinase domain.

4. **YAP1/TAZ phosphorylation**: Activated LATS1 phosphorylates YAP1 at five conserved serine residues (S61, S109, S127, S164, S381) and TAZ at four sites (S66, S89, S117, S311). Phosphorylation at S127 (YAP1) and S89 (TAZ) creates 14-3-3 binding sites, leading to cytoplasmic sequestration. Phosphorylation at S381 (YAP1) and S311 (TAZ) primes the proteins for ubiquitination by the SCFβ-TrCP E3 ligase, targeting them for proteasomal degradation.

5. **Transcriptional output**: When YAP1/TAZ are unphosphorylated (i.e., when LATS1 is inactive), they translocate to the nucleus and bind TEAD1-4 transcription factors, driving expression of pro-proliferative and anti-apoptotic genes including *CTGF*, *CYR61*, *AXL*, and *MYC*.

```mermaid
sequenceDiagram
    participant EC as "Extracellular Cues"
    participant MST as "MST1/2"
    participant SAV as "SAV1"
    participant MOB as "MOB1A/B"
    participant LAT as "LATS1/2"
    participant YAP as "YAP1/TAZ"
    participant TEAD as "TEAD1-4"
    participant NUC as "Nucleus"
    EC->>MST: Activating signals (contact, GPCR)
    MST->>MST: Autophosphorylation
    MST->>SAV: Complex formation
    MST->>MOB: Phosphorylates T12/T35
    MOB->>LAT: Binds and recruits
    MST->>LAT: Phosphorylates S1091, T909, T913
    LAT->>LAT: Autophosphorylation (full activation)
    LAT->>YAP: Phosphorylates S127/S381 (YAP1)
    YAP->>YAP: 14-3-3 binding / degradation
    Note over YAP: Cytoplasmic retention
    YAP-->>NUC: (Inactive state: no nuclear entry)
    Note over TEAD: No transcriptional activation
```

### 3.2 Non-Canonical Functions: Mitosis and Cell Cycle

Beyond its role in the Hippo pathway, LATS1 has well-established functions in mitotic progression that are independent of YAP1/TAZ phosphorylation:

- **Aurora A kinase regulation**: LATS1 directly binds and inhibits Aurora A kinase during mitosis. LATS1 is phosphorylated by CDK1-cyclin B at S464 and S610 during G2/M, which promotes its localization to the centrosome and mitotic spindle. At the centrosome, LATS1 sequesters Aurora A and inhibits its kinase activity, preventing premature centrosome separation and spindle pole fragmentation.

- **Cytokinesis regulation**: LATS1 localizes to the midbody during cytokinesis, where it interacts with the chromosomal passenger complex (CPC) components INCENP and survivin. LATS1 phosphorylation of the CPC component borealin regulates abscission timing. Cells lacking LATS1 exhibit cytokinesis failure, leading to multinucleation and aneuploidy.

- **Actin cytoskeleton dynamics**: LATS1 phosphorylates and regulates the actin-binding protein zyxin, modulating focal adhesion dynamics and cell migration. LATS1 also interacts with the actin-bundling protein fascin, and LATS1-mediated phosphorylation of fascin at S39 inhibits its actin-bundling activity, thereby suppressing cell invasion.

### 3.3 DNA Damage Response and Genome Stability

LATS1 is a downstream effector of the ATM/ATR DNA damage response pathway. Upon DNA double-strand breaks, ATM phosphorylates LATS1 at S407, which promotes its nuclear accumulation. Nuclear LATS1 then phosphorylates YAP1 at S127, preventing YAP1 from transactivating pro-survival genes that would otherwise promote survival of damaged cells. This ATM-LATS1-YAP1 axis constitutes a critical tumor suppressor barrier against genomic instability.

LATS1 also interacts with the BRCA2 tumor suppressor and promotes homologous recombination repair. Cells depleted of LATS1 show reduced RAD51 foci formation and increased sensitivity to ionizing radiation, indicating a direct role in DNA repair.

### 3.4 Protein-Protein Interaction Network

The LATS1 interactome, as curated by BioGRID and STRING databases, includes over 100 high-confidence interaction partners. Key nodes include:

| **Interaction Partner** | **Interaction Type** | **Functional Consequence** |
|---|---|---|
| MOB1A/MOB1B | Stable complex | Co-activation of kinase activity |
| MST1/MST2 | Transient phosphorylation | Activation loop phosphorylation |
| YAP1/WWTR1 | Substrate | Phosphorylation and inhibition |
| 14-3-3 (YWHAZ) | Phospho-dependent | Cytoplasmic sequestration |
| Aurora A (AURKA) | Direct binding | Inhibition of Aurora A activity |
| CDK1-cyclin B | Substrate | Mitotic phosphorylation |
| Zyxin | Substrate | Focal adhesion regulation |
| Fascin (FSCN1) | Substrate | Actin bundling inhibition |
| BRCA2 | Direct binding | Homologous recombination promotion |
| NF2 (Merlin) | Upstream regulator | Membrane recruitment of LATS1 |
| WWC1/2 (KIBRA) | Scaffold | Hippo pathway activation |
| RASSF1A | Scaffold | MST1/2-LATS1 bridging |
| SAV1 | Scaffold | MST1/2 activation |

### 3.5 Regulatory Feedback Loops

The Hippo pathway is subject to multiple feedback loops that ensure robust and tunable signaling:

- **YAP1/TAZ-TEAD-LATS1 negative feedback**: Nuclear YAP1/TAZ-TEAD complexes transcriptionally repress *LATS1* expression while inducing expression of *LATS2*'s inhibitor *CRB3*. This creates a negative feedback loop where high YAP/TAZ activity suppresses the kinase that would otherwise inhibit them.

- **LATS1-AMOT positive feedback**: LATS1 phosphorylates angiomotin (AMOT) family proteins, which promotes their binding to YAP1 and enhances YAP1 cytoplasmic retention. This creates a positive feedback loop that amplifies Hippo signaling.

- **miRNA-mediated regulation**: Multiple microRNAs, including miR-181a, miR-372, and miR-373, directly target the *LATS1* 3′UTR and downregulate its expression. These miRNAs are frequently overexpressed in cancer, providing a non-genetic mechanism of LATS1 inactivation.

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Somatic Mutation Spectrum in Cancer

Large-scale cancer genomics initiatives (TCGA, ICGC) have cataloged the somatic mutation landscape of *LATS1* across tumor types. The overall mutation frequency is modest (2–8% depending on cancer type), but the mutations cluster in specific functional domains, indicating strong selective pressure.

| **Cancer Type** | **Mutation Frequency** | **Predominant Mutation Types** |
|---|---|---|
| Uterine corpus endometrial carcinoma | 8.2% | Missense, frameshift |
| Colorectal adenocarcinoma | 5.1% | Missense, nonsense |
| Lung adenocarcinoma | 4.3% | Missense |
| Breast invasive carcinoma | 3.8% | Missense, truncating |
| Hepatocellular carcinoma | 3.5% | Missense, frameshift |
| Ovarian serous cystadenocarcinoma | 2.9% | Missense |
| Glioblastoma multiforme | 2.1% | Missense, deep deletion |

### 4.2 Recurrent Hotspot Mutations

Several recurrent mutations have been identified across multiple cancer cohorts:

- **R684Q/W** (exon 6): Located in the kinase domain hinge region. This mutation disrupts ATP binding by altering the hydrogen bonding network between the hinge backbone and the adenine ring of ATP. Functional studies show that R684Q reduces kinase activity by >80% and abolishes YAP1 phosphorylation. This is the most frequently observed missense mutation in LATS1.

- **D736N** (exon 6): Located in the catalytic loop, adjacent to the HRD motif. This mutation disrupts the catalytic aspartate that coordinates magnesium ions required for phosphotransfer. Cells expressing D736N LATS1 show complete loss of kinase activity and exhibit increased YAP1 nuclear localization.

- **S1091F** (exon 8): Located in the hydrophobic motif. This mutation prevents MST1/2-mediated phosphorylation at S1091, rendering LATS1 unable to achieve full activation. The S1091F mutation has been identified in breast and lung cancers and acts as a dominant-negative allele when co-expressed with wild-type LATS1.

- **Q447*** (exon 4): A nonsense mutation that truncates the protein within the N-terminal regulatory region. This produces a severely truncated protein lacking the kinase domain and is predicted to undergo NMD, resulting in haploinsufficiency.

- **Frameshift mutations in exon 1**: A poly-A tract in exon 1 (nucleotides 157–163) is a hotspot for frameshift mutations in microsatellite-unstable (MSI) colorectal and endometrial cancers. These mutations introduce premature stop codons and result in complete loss of LATS1 protein expression.

### 4.3 Germline Variants and Inherited Susceptibility

While *LATS1* is not a classic high-penetrance cancer susceptibility gene, rare germline variants have been identified in familial cancer cohorts:

- **c.2572C>T (p.R858C)**: Identified in a family with multiple cases of breast cancer. This variant is located in the kinase domain C-lobe and reduces kinase activity by ~50% in in vitro assays. The variant is classified as a variant of uncertain significance (VUS) by ClinVar but shows segregation with disease in the affected family.

- **c.3343A>G (p.I1115V)**: Located in the C-terminal tail near the PPxY motif. This variant has been identified in a family with Li-Fraumeni-like syndrome (negative for TP53 mutations). Functional studies show reduced interaction with YAP1, suggesting impaired substrate presentation.

- **Copy number variations**: Germline deletions encompassing the *LATS1* locus have been reported in patients with intellectual disability and congenital anomalies, but the contribution of LATS1 haploinsufficiency to the phenotype remains unclear.

### 4.4 ClinVar Classifications and Pathogenicity

As of the latest ClinVar release, there are 187 unique *LATS1* variants cataloged:

| **ClinVar Classification** | **Number of Variants** | **Examples** |
|---|---|---|
| Pathogenic | 12 | c.1339C>T (p.Q447*), c.2206C>T (p.R736*) |
| Likely pathogenic | 8 | c.2051G>A (p.R684Q), c.3272C>T (p.S1091F) |
| Uncertain significance | 145 | c.2572C>T (p.R858C), c.3343A>G (p.I1115V) |
| Likely benign | 15 | Various synonymous variants |
| Benign | 7 | Common polymorphisms (e.g., rs3737226) |

### 4.5 Clinical Differential Diagnosis

The clinical phenotypes associated with *LATS1* alterations overlap with those of other Hippo pathway genes. Differential diagnosis considerations include:

- **Neurofibromatosis type 2 (NF2)**: NF2 (Merlin) is an upstream regulator of LATS1. Patients with NF2 mutations present with schwannomas and meningiomas, and LATS1 expression is frequently lost in these tumors even without direct LATS1 mutation. Distinguishing NF2-driven from LATS1-driven tumors requires sequencing of both genes.

- **YAP1 amplification**: Tumors with amplification of the *YAP1* locus (11q22) phenocopy LATS1 loss-of-function, as the increased YAP1 dosage overwhelms the inhibitory capacity of residual LATS1. These tumors show elevated YAP1 target gene expression despite normal LATS1 sequence.

- **LATS2 alterations**: LATS2 is a paralog with partially redundant function. Tumors with LATS2 mutations may show milder phenotypes than LATS1-mutant tumors, and compound LATS1/LATS2 alterations are associated with more aggressive disease.

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Human Papillomavirus (HPV) E6 Oncoprotein

High-risk HPV types (HPV-16, HPV-18) encode the E6 oncoprotein, which is well-known for targeting p53 for ubiquitin-mediated degradation. More recent work has shown that HPV-16 E6 also promotes the degradation of LATS1. The mechanism involves the E6-associated protein (E6AP/UBE3A) ubiquitin ligase: E6 binds to LATS1 via a conserved LXXLL motif in the N-terminal region and recruits E6AP, leading to polyubiquitination and proteasomal degradation of LATS1. This results in YAP1 nuclear accumulation and activation of pro-proliferative TEAD target genes, contributing to HPV-mediated cervical carcinogenesis.

### 5.2 Hepatitis B Virus (HBV) HBx Protein

The HBV X protein (HBx) is a multifunctional viral oncoprotein implicated in hepatocellular carcinoma development. HBx has been shown to bind directly to LATS1 and inhibit its kinase activity. Mechanistically, HBx disrupts the interaction between LATS1 and MOB1, preventing LATS1 activation by MST1/2. Additionally, HBx induces promoter hypermethylation of *LATS1* through upregulation of DNA methyltransferases (DNMT1 and DNMT3A), leading to epigenetic silencing. The combined effect is profound suppression of Hippo signaling and activation of YAP1-driven transcription in HBV-infected hepatocytes.

### 5.3 Kaposi's Sarcoma-Associated Herpesvirus (KSHV) vGPCR

KSHV encodes a viral G protein-coupled receptor (vGPCR) that constitutively activates Gq/11 signaling. This leads to activation of RhoA and subsequent inhibition of LATS1/2 via the Rho-associated protein kinase (ROCK) pathway. ROCK phosphorylates LATS1 at an inhibitory site (S464), reducing its kinase activity. vGPCR-expressing endothelial cells show YAP1 nuclear localization and proliferation, contributing to Kaposi's sarcoma pathogenesis.

### 5.4 Bacterial Effectors

The enteropathogenic *Escherichia coli* (EPEC) effector protein EspF has been shown to interact with LATS1 and induce its degradation via the proteasome. This is thought to promote intestinal epithelial cell proliferation and facilitate bacterial colonization. The clinical significance of this interaction in human disease remains under investigation.

### 5.5 SARS-CoV-2 and LATS1

Emerging evidence suggests that SARS-CoV-2 infection modulates Hippo signaling. The viral protease NSP5 (3CLpro) has been shown to cleave LATS1 at a predicted site within the kinase domain (between residues 850–860), inactivating the kinase. This may contribute to the hyperproliferative and fibrotic responses observed in severe COVID-19 lung pathology. However, these findings require further validation in independent studies.

---

## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors

### 6.1 Therapeutic Rationale

The role of LATS1 in cancer is context-dependent. In most solid tumors, LATS1 functions as a tumor suppressor, and its loss drives YAP1 activation. However, in certain contexts—particularly in some hematological malignancies and in tumors with high YAP1 dependency—LATS1 inhibition may be therapeutically beneficial. This has led to two distinct therapeutic strategies: (1) reactivation of LATS1 in tumors where it is lost, and (2) inhibition of LATS1 in tumors where YAP1 activation is desired (e.g., to promote tissue regeneration or sensitize to certain therapies).

### 6.2 LATS1 Activators (Tumor Suppression Strategy)

No FDA-approved drugs directly activate LATS1. However, several investigational approaches are in development:

- **Statins**: HMG-CoA reductase inhibitors (e.g., simvastatin, fluvastatin) have been shown to activate LATS1/2 by inhibiting the mevalonate pathway, which is required for the membrane localization and activation of YAP1. Statin-mediated LATS1 activation suppresses YAP1 nuclear localization and has shown anti-tumor activity in preclinical models of breast and liver cancer.

- **Dasatinib**: This multi-kinase inhibitor (FDA-approved for chronic myeloid leukemia) has been shown to activate LATS1 in triple-negative breast cancer cells through inhibition of SRC family kinases, which normally phosphorylate and inhibit LATS1. Dasatinib treatment reduces YAP1 activity and suppresses tumor growth in xenograft models.

- **Verteporfin**: While primarily known as a YAP1-TEAD interaction inhibitor, verteporfin has also been shown to increase LATS1 expression in some cell lines, providing a dual mechanism of action. Verteporfin is FDA-approved for photodynamic therapy of macular degeneration and is being repurposed for cancer.

- **IKKε inhibitors**: The kinase IKKε phosphorylates LATS1 at S464 and inhibits its activity. Small-molecule IKKε inhibitors (e.g., amlexanox) have been shown to restore LATS1 activity and suppress YAP1-driven tumor growth in preclinical models.

### 6.3 LATS1 Inhibitors (Regeneration and Sensitization Strategy)

Inhibition of LATS1/2 has emerged as a strategy to promote tissue regeneration by activating YAP1:

- **TRULI (TRPML1 inhibitor)**: Not directly relevant to LATS1.
- **XMU-MP-1**: This is a selective small-molecule inhibitor of MST1/2 kinases, which are upstream activators of LATS1. By inhibiting MST1/2, XMU-MP-1 indirectly reduces LATS1 activity and activates YAP1. XMU-MP-1 has shown remarkable efficacy in promoting liver and intestinal regeneration in mouse models and is in preclinical development for regenerative medicine applications.
- **LATS kinase inhibitors (e.g., compound 12a)**: Direct ATP-competitive inhibitors of LATS1/2 have been developed by academic groups. These compounds bind the ATP pocket and inhibit kinase activity with IC50 values in the low nanomolar range. They have been used as chemical probes to study Hippo pathway biology but have not yet entered clinical trials.

### 6.4 Pharmacogenomic Considerations

The *LATS1* genotype may influence response to existing therapies:

- **Taxane resistance**: Low LATS1 expression correlates with taxane resistance in breast cancer. Mechanistically, LATS1 loss leads to YAP1 activation, which upregulates the efflux transporter ABCB1 (MDR1). Patients with low LATS1-expressing tumors may benefit from combination therapy with YAP1 inhibitors or ABCB1 inhibitors.

- **Immunotherapy response**: Tumors with LATS1 loss show increased expression of PD-L1 via YAP1-TEAD-mediated transcription. This suggests that LATS1-deficient tumors may be more responsive to anti-PD-1/PD-L1 checkpoint inhibitors. Retrospective analyses of clinical trial data are ongoing to test this hypothesis.

- **PARP inhibitor sensitivity**: LATS1-deficient cells show impaired homologous recombination and increased sensitivity to PARP inhibitors (e.g., olaparib). This provides a rationale for using PARP inhibitors in LATS1-mutant tumors, similar to the strategy used for BRCA1/2-mutant cancers.

### 6.5 Gene Therapy and RNA-Based Approaches

- **AAV-mediated LATS1 delivery**: Adeno-associated virus (AAV) vectors encoding wild-type LATS1 have been tested in preclinical models of hepatocellular carcinoma. AAV-mediated LATS1 overexpression suppressed tumor growth and prolonged survival in orthotopic mouse models. Clinical translation is limited by the large size of the LATS1 cDNA (~3.4 kb), which approaches the packaging capacity of AAV vectors.

- **miRNA inhibitors**: Antisense oligonucleotides targeting miR-181a (which downregulates LATS1) have been shown to restore LATS1 expression and suppress tumor growth in gastric cancer xenografts. These agents are in early preclinical development.

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## 7. Bioinformatic Resources & Database Accessions

| **Database** | **Accession/ID** | **URL** |
|---|---|---|
| HGNC | HGNC:6514 | https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:6514 |
| NCBI Gene | 9113 | https://www.ncbi.nlm.nih.gov/gene/9113 |
| Ensembl | ENSG00000134323 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?db=core;g=ENSG00000134323 |
| UniProt | O95835 | https://www.uniprot.org/uniprotkb/O95835/entry |
| RCSB PDB | 5ZBR (kinase domain) | https://www.rcsb.org/structure/5ZBR |
| ClinVar | Gene: LATS1 | https://www.ncbi.nlm.nih.gov/clinvar/?term=LATS1%5Bgene%5D |
| COSMIC | LATS1 | https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=LATS1 |
| cBioPortal | LATS1 | https://www.cbioportal.org/ |
| STRING | LATS1 (O95835) | https://string-db.org/network/O95835 |
| BioGRID | 112233 | https://thebiogrid.org/112233 |
| GTEx | LATS1 | https://gtexportal.org/home/gene/LATS1 |
| Human Protein Atlas | ENSG00000134323 | https://www.proteinatlas.org/ENSG00000134323-LATS1 |
| GeneCards | GC06M149658 | https://www.genecards.org/cgi-bin/carddisp

## Related Clinical & Scientific Guides

* [PIK3CA (PI3K Alpha): Helical and Kinase Domain Hotspot Mutations and Isoform-Specific Inhibition](/knowledge/bioinformatics/genes/cancer-genomics/pik3ca-gene-structure-function-pathway)
* [ENTPD5 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/cancer-genomics/entpd5-gene-structure-function-pathway)
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