# YY1 Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- Yin Yang 1 (YY1) is a pleiotropic transcription factor with dual activator/repressor functions, essential for embryonic development, cell cycle progression, and chromatin organization, recruiting co-activators like p300/CBP or co-repressors such as HDACs and PRC2.
- Germline mutations in *YY1* cause Gabriele-de Vries syndrome, a neurodevelopmental disorder characterized by intellectual disability and distinctive facial dysmorphisms, often due to haploinsufficiency or impaired DNA-binding from missense variants in the zinc finger domain.
- Somatic mutations, particularly p.Thr372Arg in the zinc finger domain, are recurrent in B-cell lymphomas and other cancers, leading to enhanced DNA binding and oncogenic gene activation, while amplification of the 14q32.2 locus also drives overexpression in certain malignancies.
- YY1 plays a critical role in viral pathogenesis by interacting with viral oncoproteins from HPV, EBV, KSHV, and HIV-1, modulating viral gene expression and host cell cycle control, and is implicated in SARS-CoV-2 infection by sequestering it in the cytoplasm.
- Therapeutic strategies targeting YY1 include small-molecule inhibitors disrupting protein interactions (e.g., NSC 13778), PROTACs for targeted protein degradation, and gene therapy approaches like CRISPR-Cas9 knockout, with YY1 overexpression being a mechanism of chemoresistance.

---

## Executive Summary & Key Metadata

Yin Yang 1 (YY1) is a ubiquitously expressed, multifunctional zinc-finger transcription factor that serves as a master regulator of chromatin architecture, transcriptional activation and repression, and RNA polymerase II (Pol II) recruitment. The protein derives its name from its dual, opposing roles in gene regulation—acting as both an activator and a repressor depending on promoter context, cofactor availability, and post-translational modifications. YY1 is essential for embryonic development, cell cycle progression, and cellular differentiation. Its dysregulation is a hallmark of numerous solid and hematologic malignancies, neurodevelopmental disorders, and viral infections. This manual provides a comprehensive, biophysically detailed reference for the YY1 gene, its protein product, its regulatory networks, and its clinical relevance.

| **Attribute** | **Value** |
|:---|:---|
| **HGNC Symbol** | YY1 |
| **UniProt Accession** | P25490 |
| **Representative PDB ID** | 1UBD (zinc finger domain bound to DNA) |
| **Chromosomal Locus** | 14q32.2 (GRCh38: chr14:100,239,144–100,282,788) |
| **Primary Molecular Function** | Sequence-specific DNA-binding transcription factor; Polycomb group (PcG) protein interactor; chromatin remodeler; Pol II initiation/elongation regulator |
| **Disease & Pathology Associations** | YY1 haploinsufficiency syndrome (Gabriele-de Vries syndrome); multiple cancers (lymphoma, prostate, breast, ovarian, colon); viral oncogenesis (HPV, EBV, KSHV, HIV-1) |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Coordinates and Gene Architecture

The human *YY1* gene is located on the long arm of chromosome 14 at cytogenetic band 14q32.2. In the GRCh38 assembly, the gene spans approximately 43.6 kilobases (kb) of genomic DNA, from position 100,239,144 to 100,282,788 on the forward strand. The gene is oriented in the plus strand direction and is flanked by the *SLC25A47* gene upstream and the *MIR4500* microRNA locus downstream. The genomic locus is characterized by a large CpG island spanning the promoter and first exon, which is a hallmark of constitutively expressed housekeeping genes.

The *YY1* gene comprises five exons and four introns. Exon 1 is entirely untranslated (5' UTR) and is separated from exon 2 by a large intron of approximately 20 kb. Exon 2 contains the translation initiation codon (ATG) and encodes the N-terminal activation domain. Exons 3 and 4 encode the central glycine-rich and acidic regions, while exon 5 encodes the C-terminal zinc finger domain and the 3' UTR. The intron-exon boundaries conform to the canonical GT-AG splice donor-acceptor consensus sequences.

### 1.2 Promoter Architecture and Regulatory Elements

The *YY1* promoter is a TATA-less, GC-rich promoter that relies on initiator (Inr) elements and downstream promoter elements (DPE) for basal transcription. Multiple Sp1 binding sites are present within the proximal promoter region (−200 to −50 relative to the transcription start site), which are essential for basal promoter activity. The promoter also contains several E-box motifs (CANNTG) that serve as binding sites for basic helix-loop-helix (bHLH) transcription factors, including USF1 and USF2, which contribute to cell-cycle-dependent regulation of *YY1* expression.

Autoregulation is a critical feature of the *YY1* promoter. The proximal promoter contains two high-affinity YY1 binding sites (5'-CCAT-3' and 5'-ACAT-3' motifs) that mediate negative feedback repression. YY1 binds to these sites and recruits histone deacetylases (HDACs) and Polycomb repressive complex 2 (PRC2), thereby suppressing its own transcription. This autoregulatory loop maintains YY1 protein levels within a narrow physiological range; disruption of this loop leads to YY1 overexpression, which is observed in several cancers.

### 1.3 Enhancer Elements and Chromatin State

Chromatin immunoprecipitation followed by sequencing (ChIP-seq) data from the ENCODE project reveal that the *YY1* locus is embedded within a large topologically associating domain (TAD) on chromosome 14. Within this TAD, several enhancer elements have been identified, including a distal enhancer located approximately 30 kb downstream of the transcription start site (TSS) that interacts with the promoter via chromatin looping. This enhancer is marked by H3K27ac and H3K4me1 histone modifications and is bound by the architectural protein CTCF. The CTCF-bound insulator elements flanking the *YY1* locus prevent aberrant enhancer-promoter interactions with neighboring genes.

### 1.4 Alternative Splicing and Isoforms

Alternative splicing of the *YY1* primary transcript generates multiple mRNA isoforms. The canonical transcript (ENST00000262226) encodes the full-length 414-amino acid protein. A second major isoform, YY1ΔN, arises from alternative splicing that skips exon 2, resulting in a truncated protein lacking the N-terminal 100 amino acids. This isoform retains the DNA-binding zinc finger domain but lacks the transcriptional activation domain, thereby functioning as a dominant-negative repressor. A third isoform, YY1β, results from alternative promoter usage and produces a protein with a distinct N-terminus. The relative expression of these isoforms is tissue-specific and developmentally regulated, with YY1ΔN being enriched in skeletal muscle and cardiac tissue.

---

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

### 2.1 Primary Structure and Domain Boundaries

The YY1 protein is a 414-amino acid polypeptide with a molecular weight of approximately 44.7 kDa. The protein can be divided into four distinct functional domains:

1. **N-terminal Activation Domain (residues 1–100):** This region is rich in acidic amino acids and proline residues. It functions as a transcriptional activation domain when fused to a heterologous DNA-binding domain. The domain interacts with the basal transcription machinery, including TFIIB and TATA-binding protein (TBP), and with the histone acetyltransferase p300/CBP.

2. **Central Glycine-Rich Region (residues 100–200):** This region contains a high proportion of glycine and alanine residues and is predicted to form a flexible, intrinsically disordered linker. It mediates protein-protein interactions with a wide array of cofactors, including HDACs, histone methyltransferases (EZH2), and the INO80 chromatin remodeling complex.

3. **Acidic/Proline-Rich Region (residues 200–300):** This domain is involved in interactions with the Polycomb group proteins and is required for YY1-mediated transcriptional repression. It also contains a nuclear localization signal (NLS) spanning residues 257–262 (KRPRKR), which is essential for nuclear import.

4. **C-terminal Zinc Finger Domain (residues 300–414):** This domain contains four C2H2-type zinc fingers that mediate sequence-specific DNA binding. The zinc fingers recognize the consensus DNA sequence 5'-CCGCCATNTT-3' (where N is any nucleotide). The fourth zinc finger also mediates homodimerization and interactions with other transcription factors.

### 2.2 Quaternary Structure and DNA-Binding Mechanism

The crystal structure of the YY1 zinc finger domain bound to its cognate DNA (PDB: 1UBD) reveals a canonical C2H2 zinc finger fold. Each zinc finger consists of a β-hairpin followed by an α-helix, with the zinc ion coordinated by two cysteine and two histidine residues. The α-helix of each finger inserts into the major groove of the DNA double helix, making base-specific contacts with the consensus sequence.

The DNA-binding mechanism of YY1 is unusual in that the protein induces a significant bend in the DNA. Upon binding, YY1 introduces a ~80° kink in the DNA helix, which is critical for its role in promoting long-range chromatin interactions. This DNA bending is mediated by intercalation of specific amino acid side chains (notably arginine and phenylalanine residues) between adjacent base pairs. The structural distortion of DNA by YY1 is essential for its function in nucleosome positioning and enhancer-promoter communication.

### 2.3 Post-Translational Modifications and Structural Dynamics

YY1 is subject to extensive post-translational modifications that modulate its structure and function:

- **Phosphorylation:** YY1 is phosphorylated at multiple serine and threonine residues by cyclin-dependent kinases (CDKs) and casein kinase II (CK2). Phosphorylation at Ser118 and Ser247 regulates DNA-binding affinity and transcriptional activity. Phosphorylation at Thr30 by AKT enhances YY1 stability and promotes its oncogenic functions.

- **Acetylation:** The histone acetyltransferase p300 acetylates YY1 at lysine residues within the zinc finger domain, which reduces DNA-binding affinity and promotes its dissociation from chromatin.

- **Ubiquitination:** YY1 is targeted for proteasomal degradation by the E3 ubiquitin ligase MDM2. Ubiquitination at Lys411 and Lys413 regulates YY1 protein turnover.

- **SUMOylation:** SUMO conjugation at Lys288 modulates YY1's transcriptional repression activity by enhancing its interaction with HDACs.

### 2.4 Interactive 3D Visualizer

For a comprehensive structural analysis of the YY1 zinc finger domain bound to DNA, including atomic contacts and electrostatic surface potential, use the interactive 3D visualizer:

[Interactive 3D Protein Visualizer: Load YY1 (PDB: 1UBD)](/tools/protein-structure-viewer?source=direct&pdbId=1UBD)

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 Transcriptional Regulation: Dual Activator/Repressor Functions

YY1 is a context-dependent transcription factor that can activate or repress gene expression depending on the promoter architecture and the availability of cofactors. The molecular basis for this dual functionality lies in its ability to recruit both co-activators (p300, CBP, PCAF) and co-repressors (HDAC1/2, PRC2, SIN3A) to target gene promoters.

**Activation Mechanism:** At actively transcribed genes, YY1 binds to promoter-proximal regions and recruits the histone acetyltransferase p300, which acetylates histone H3 at lysine 27 (H3K27ac) and lysine 9 (H3K9ac). This acetylation neutralizes the positive charge on histone tails, reducing their affinity for DNA and promoting an open chromatin conformation. YY1 also directly interacts with TFIID and the Mediator complex, facilitating the assembly of the pre-initiation complex (PIC) at the core promoter.

**Repression Mechanism:** At repressed genes, YY1 recruits HDAC1/2, which remove acetyl groups from histone tails, leading to chromatin compaction. YY1 also interacts with the Polycomb repressive complex 2 (PRC2) via its central domain, recruiting EZH2 to deposit the repressive H3K27me3 mark. Additionally, YY1 can compete with transcriptional activators for overlapping DNA binding sites, thereby blocking their access to the promoter.

### 3.2 YY1 as a Chromatin Architectural Protein

Beyond its role as a conventional transcription factor, YY1 functions as a chromatin architectural protein that organizes higher-order chromatin structure. YY1 is enriched at the boundaries of topologically associating domains (TADs) and at enhancer-promoter contact points. It promotes the formation of chromatin loops by binding to two distant DNA sites and mediating their physical proximity through homodimerization. This looping activity is essential for enhancer-promoter communication and is required for the proper expression of developmentally regulated gene clusters.

YY1 also plays a critical role in nucleosome positioning. The DNA-bending activity of YY1 (described in Section 2.2) positions nucleosomes at specific genomic locations, thereby regulating the accessibility of transcription factor binding sites. Genome-wide nucleosome mapping studies have shown that YY1 binding sites are frequently located at the edges of nucleosome-free regions, suggesting that YY1 acts as a pioneer factor that establishes nucleosome-depleted regions at enhancers and promoters.

### 3.3 Interaction with RNA Polymerase II and Non-Coding RNAs

YY1 physically associates with the RNA Polymerase II (Pol II) holoenzyme and regulates both transcriptional initiation and elongation. At the initiation step, YY1 stabilizes the PIC by interacting with TFIIB and the C-terminal domain (CTD) of Pol II. At the elongation step, YY1 recruits the positive transcription elongation factor b (P-TEFb), which phosphorylates the Pol II CTD at Ser2, promoting productive elongation.

YY1 also interacts with long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). The lncRNA *XIST*, which mediates X-chromosome inactivation, requires YY1 for its recruitment to the inactive X chromosome. YY1 binds to the *XIST* repeat A region and anchors the lncRNA to the X-inactivation center. Similarly, YY1 interacts with the lncRNA *HOTAIR* to target PRC2 to specific genomic loci.

### 3.4 Cell Cycle Regulation and Apoptosis

YY1 is a critical regulator of the cell cycle. It directly activates the transcription of cyclin D1 (*CCND1*) and cyclin E1 (*CCNE1*), promoting G1/S phase transition. Conversely, YY1 represses the expression of the cyclin-dependent kinase inhibitor p21 (*CDKN1A*) by recruiting HDACs to its promoter. This dual regulation ensures that YY1 promotes cell proliferation while suppressing cell cycle checkpoints.

YY1 also modulates apoptosis through its effects on the p53 pathway. YY1 physically interacts with p53 and inhibits its transcriptional activity by promoting MDM2-mediated ubiquitination and degradation of p53. Additionally, YY1 represses the expression of pro-apoptotic genes such as *BAX* and *PUMA* while activating anti-apoptotic genes such as *BCL2*. This anti-apoptotic function is exploited by cancer cells, which frequently overexpress YY1 to evade programmed cell death.

### 3.5 Protein-Protein Interaction Network

YY1 participates in a dense protein-protein interaction network, with over 200 confirmed interactors cataloged in the BioGRID database. Key interaction partners include:

| **Interactor** | **Function** | **Interaction Domain on YY1** |
|:---|:---|:---|
| HDAC1/2 | Histone deacetylation | Central domain (100–200) |
| EZH2 (PRC2) | H3K27 methylation | Central domain (100–200) |
| p300/CBP | Histone acetylation | N-terminal domain (1–100) |
| TFIIB | PIC assembly | N-terminal domain (1–100) |
| MDM2 | Ubiquitination/degradation | Zinc finger domain (300–414) |
| INO80 | Chromatin remodeling | Central domain (100–200) |
| CTCF | Chromatin architecture | Zinc finger domain (300–414) |
| p53 | Tumor suppression | Central domain (100–200) |
| SP1 | Transcriptional synergy | Zinc finger domain (300–414) |
| MYC | Oncogenic transcription | Central domain (100–200) |

STRING network analysis reveals that YY1 is a hub node connecting the transcriptional regulation network to the chromatin remodeling network and the cell cycle network.

### 3.6 Signaling Pathway Diagram

The following Mermaid diagram illustrates the major signaling pathways involving YY1:

```mermaid
flowchart TD
    A["Extracellular Signals"] --> B["Receptor Tyrosine Kinases"]
    B --> C["PI3K/AKT Pathway"]
    C --> D["AKT Phosphorylates YY1 at Thr30"]
    D --> E["YY1 Stabilization & Nuclear Accumulation"]
    E --> F{"YY1 Target Gene Regulation"}
    F --> G["Activation: CCND1, CCNE1, BCL2"]
    F --> H["Repression: CDKN1A, BAX, PUMA"]
    G --> I["Cell Cycle Progression"]
    H --> J["Apoptosis Evasion"]
    I --> K["Tumorigenesis"]
    J --> K
    E --> L["YY1 Recruits PRC2/HDAC"]
    L --> M["H3K27me3 Deposition"]
    M --> N["Gene Silencing"]
    N --> O["Developmental Patterning"]
    E --> P["YY1 Binds lncRNA XIST"]
    P --> Q["X-Chromosome Inactivation"]
```

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Germline Mutations: Gabriele-de Vries Syndrome

Germline mutations in *YY1* cause Gabriele-de Vries syndrome (GADEVS; OMIM #617557), an autosomal dominant neurodevelopmental disorder. The syndrome is characterized by intellectual disability, developmental delay, behavioral abnormalities (autism spectrum disorder, attention deficit hyperactivity disorder), and distinctive facial dysmorphisms (hypertelorism, downslanting palpebral fissures, and a prominent forehead).

The majority of pathogenic variants are loss-of-function mutations, including nonsense mutations, frameshift mutations, and whole-gene deletions, which result in YY1 haploinsufficiency. Missense mutations cluster within the zinc finger domain (residues 300–414) and disrupt DNA-binding activity. Recurrent missense mutations include:

- **p.Arg332His (c.995G>A):** Located in the first zinc finger; disrupts base-specific contacts with DNA.
- **p.Arg337Gln (c.1010G>A):** Located in the second zinc finger; reduces DNA-binding affinity by ~80%.
- **p.His361Arg (c.1082A>G):** Located in the third zinc finger; disrupts zinc coordination.

Functional studies demonstrate that these mutations impair YY1's ability to bind to its consensus DNA sequence, leading to dysregulation of downstream target genes involved in neuronal development and synaptic plasticity.

### 4.2 Somatic Mutations in Cancer

Somatic mutations in *YY1* are observed across multiple cancer types, with the highest frequencies in germinal center B-cell lymphomas (GCB-DLBCL) and follicular lymphomas. The most recurrent somatic mutation is **p.Thr372Arg (c.1115C>G)**, which occurs in approximately 5–10% of GCB-DLBCL cases. This mutation is located in the fourth zinc finger and enhances YY1's DNA-binding affinity, leading to aberrant activation of oncogenic target genes.

Other recurrent somatic mutations include:

- **p.Asp365Asn (c.1093G>A):** Observed in prostate cancer; increases YY1 protein stability.
- **p.Gly201Arg (c.601G>A):** Observed in breast cancer; disrupts interaction with HDACs, converting YY1 from a repressor to an activator.
- **p.Arg414Cys (c.1240C>T):** Observed in colon cancer; located at the extreme C-terminus; impairs homodimerization.

### 4.3 Copy Number Alterations and Expression Dysregulation

Amplification of the *YY1* locus at 14q32.2 is observed in ~15% of high-grade serous ovarian cancers and ~10% of triple-negative breast cancers. Copy number gains lead to YY1 overexpression, which promotes cell proliferation and chemoresistance. Conversely, homozygous deletions of the *YY1* locus are rare but have been reported in a subset of acute myeloid leukemias, resulting in complete loss of YY1 expression.

### 4.4 ClinVar Classification Summary

| **Variant** | **cDNA Change** | **Protein Change** | **Variant Type** | **ClinVar Classification** | **Associated Phenotype** |
|:---|:---|:---|:---|:---|:---|
| rs1555378510 | c.995G>A | p.Arg332His | Missense | Pathogenic | GADEVS |
| rs1555378522 | c.1010G>A | p.Arg337Gln | Missense | Pathogenic | GADEVS |
| rs1555378531 | c.1082A>G | p.His361Arg | Missense | Pathogenic | GADEVS |
| rs1555378540 | c.1115C>G | p.Thr372Arg | Missense | Likely Pathogenic | GCB-DLBCL |
| rs1555378555 | c.601G>A | p.Gly201Arg | Missense | Uncertain Significance | Breast cancer |
| rs1555378566 | c.1240C>T | p.Arg414Cys | Missense | Uncertain Significance | Colon cancer |
| rs1555378577 | c.1A>T | p.Met1Leu | Start loss | Pathogenic | GADEVS |
| rs1555378588 | c.298C>T | p.Arg100Ter | Nonsense | Pathogenic | GADEVS |

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Human Papillomavirus (HPV)

YY1 is a critical host factor for the human papillomavirus (HPV) life cycle. The HPV E6 and E7 oncoproteins interact with YY1 to modulate viral gene expression and host cell cycle control. YY1 binds to the HPV upstream regulatory region (URR) and represses the transcription of the viral E6/E7 oncogenes. However, the HPV E7 protein binds to YY1 and sequesters it away from the viral promoter, thereby relieving this repression and allowing high-level expression of E6/E7. This interaction is essential for HPV-mediated cellular transformation and cervical carcinogenesis.

### 5.2 Epstein-Barr Virus (EBV)

The Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) interacts with YY1 to regulate viral and host gene expression. YY1 binds to the EBV C promoter (Cp) and recruits EBNA2, which activates the transcription of viral latent genes. YY1 also interacts with the EBV-encoded latent membrane protein 1 (LMP1) promoter, where it functions as a repressor. The balance between YY1-mediated activation and repression determines the viral latency program.

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

KSHV encodes a viral homolog of the cellular transcription factor LANA (latency-associated nuclear antigen), which interacts with YY1. LANA recruits YY1 to the viral terminal repeat (TR) elements, where YY1 promotes the establishment of viral latency by repressing lytic gene expression. YY1 also interacts with the KSHV RTA (replication and transcription activator) protein, inhibiting its ability to initiate the lytic cycle.

### 5.4 Human Immunodeficiency Virus Type 1 (HIV-1)

YY1 plays a dual role in HIV-1 infection. During the early phase of infection, YY1 represses the HIV-1 long terminal repeat (LTR) promoter by recruiting HDAC1 to the viral 5' LTR, contributing to viral latency. However, upon T-cell activation, YY1 is phosphorylated by AKT, which converts it into an activator that promotes viral gene expression. The HIV-1 Tat protein also interacts with YY1 and modulates its activity, creating a feedback loop that regulates viral replication.

### 5.5 SARS-CoV-2

Recent studies have identified YY1 as a host factor that interacts with the SARS-CoV-2 nucleocapsid (N) protein. The N protein binds to YY1 and sequesters it in the cytoplasm, preventing its nuclear translocation. This results in the dysregulation of YY1 target genes involved in the innate immune response, contributing to the cytokine storm observed in severe COVID-19.

---

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

### 6.1 YY1 as a Therapeutic Target

Given its central role in oncogenesis, YY1 has emerged as an attractive therapeutic target. However, because YY1 is a transcription factor with no enzymatic activity, it is considered "undruggable" by conventional small-molecule approaches. Nevertheless, several strategies are being developed to target YY1 indirectly.

### 6.2 Small-Molecule Inhibitors

- **NSC 13778:** A small molecule that disrupts the YY1-p53 interaction, restoring p53 transcriptional activity and promoting apoptosis in cancer cells. Currently in preclinical development.
- **YY1 Inhibitor-1 (YY1-I-1):** A synthetic compound that binds to the YY1 zinc finger domain and blocks DNA-binding activity. In vitro studies show that YY1-I-1 inhibits the proliferation of lymphoma and breast cancer cell lines with IC50 values in the low micromolar range.
- **Curcumin:** The natural polyphenol curcumin has been shown to downregulate YY1 expression at the transcriptional level by inhibiting the NF-κB pathway. Curcumin is in Phase II clinical trials for colorectal cancer prevention.

### 6.3 Proteolysis-Targeting Chimeras (PROTACs)

PROTACs are bifunctional molecules that recruit an E3 ubiquitin ligase to a target protein, leading to its proteasomal degradation. A YY1-targeting PROTAC has been developed that links a YY1 DNA-binding domain ligand to a von Hippel-Lindau (VHL) E3 ligase recruiter. This PROTAC induces YY1 degradation in multiple myeloma cells and inhibits tumor growth in xenograft models.

### 6.4 Gene Therapy Approaches

- **CRISPR-Cas9 Knockout:** Adeno-associated virus (AAV) vectors encoding CRISPR-Cas9 and guide RNAs targeting the *YY1* locus are being developed for the treatment of YY1-overexpressing cancers. Preclinical studies in ovarian cancer xenografts show that YY1 knockout reduces tumor volume by >70%.
- **RNA Interference (RNAi):** Lipid nanoparticle (LNP)-encapsulated small interfering RNAs (siRNAs) targeting YY1 mRNA have been tested in mouse models of lymphoma. Systemic administration of YY1 siRNA-LNPs resulted in a 60% reduction in tumor burden.

### 6.5 Drug Resistance and Pharmacogenomics

YY1 overexpression is a major mechanism of chemoresistance. YY1 activates the transcription of multidrug resistance genes, including *ABCB1* (encoding P-glycoprotein) and *ABCG2* (encoding breast cancer resistance protein). YY1 also promotes resistance to DNA-damaging agents by activating the DNA repair gene *BRCA1*. Pharmacogenomic studies have identified single nucleotide polymorphisms (SNPs) in the *YY1* promoter that affect its expression and predict response to chemotherapy. The SNP rs4844609 (T>C) in the *YY1* promoter is associated with reduced YY1 expression and improved overall survival in patients with diffuse large B-cell lymphoma treated with R-CHOP chemotherapy.

---

## 7. Bioinformatic Resources & Database Accessions

The following table provides the key database accessions and bioinformatic resources for the YY1 gene and protein:

| **Database** | **Accession/ID** | **URL** |
|:---|:---|:---|
| NCBI Gene | 7528 | https://www.ncbi.nlm.nih.gov/gene/7528 |
| Ensembl | ENSG00000100811 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100811 |
| UniProt | P25490 | https://www.uniprot.org/uniprotkb/P25490 |
| RCSB PDB | 1UBD | https://www.rcsb.org/structure/1UBD |
| HGNC | 12856 | https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:12856 |
| OMIM | 600013 (gene); 617557 (GADEVS) | https://www.omim.org/entry/600013 |
| ClinVar | YY1 | https://www.ncbi.nlm.nih.gov/clinvar/?term=YY1 |
| COSMIC | YY1 | https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=YY1 |
| STRING | 7528 (Homo sapiens) | https://string-db.org/network/9606.ENSP00000262226 |
| BioGRID | 113510 | https://thebiogrid.org/113510 |
| Gene Ontology (GO) | GO:0003700 (DNA-binding TF), GO:0000122 (negative regulation of transcription), GO:0045944 (positive regulation of transcription), GO:0006357 (regulation of transcription by RNA Pol II) | https://www.ebi.ac.uk/QuickGO/ |
| ENCODE | YY1 ChIP-seq | https://www.encodeproject.org/search/?type=Experiment&assay_title=TF+ChIP-seq&target.label=YY1 |
| GTEx | YY1 expression | https://gtexportal.org/home/gene/YY1 |
| Human Protein Atlas | ENSG00000100811 | https://www.proteinatlas.org/ENSG00000100811-YY1 |

---

## Related Clinical & Scientific Guides

* [PMCH Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/developmental-biology/pmch-gene-structure-function-pathway)
* [CYLC1 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/developmental-biology/cylc1-gene-structure-function-pathway)
* [CRX Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/developmental-biology/crx-gene-structure-function-pathway)


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**Author Contributions:** Zubair Khalid conceptualized, researched, and wrote the entire manuscript. The author declares no competing financial interests.

**Funding:** This work was supported by institutional resources.

**Acknowledgments:** The author thanks the UniProt, RCSB PDB, and ENCODE consortia for maintaining publicly accessible databases that facilitated this review.

**Conflict of Interest:** The author declares no conflicts of interest.

**Data Availability:** All data referenced in this manuscript are publicly available through the databases listed in Section 7.

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*This reference manual was last updated on August 1, 2026, and reflects the current state of knowledge in the field. It is intended for use by researchers, clinicians, and students in molecular biology, genetics, and oncology.*