### DNMT3B Gene Overview

**Gene Symbol**: DNMT3B  
**Location**: Chromosome 20 (20q11.21)  
**Gene Type**: Protein-coding  

**Function**: 
DNMT3B encodes a DNA methyltransferase involved in de novo methylation, crucial for establishing DNA methylation patterns during embryonic development, genomic imprinting, and X-chromosome inactivation. It primarily acts on nucleosomal DNA, and its function is closely linked to histone methylation. The enzyme may also play a role as a transcriptional co-repressor through interactions with various proteins, influencing gene silencing.

### 1. Associated Genes

While the summaries provided primarily mention DNMT1 and CTCFL/BORIS as related factors, DNMT3B is also associated with the following genes/proteins:

- **CBX4**: A protein that DNMT3B associates with for its transcriptional repressive functions.
- **ZHX1**: Another co-factor involved in the transcriptional repression mediated by DNMT3B.
- **BAG1**: Gene whose expression is activated in cooperation with DNMT1 and other factors.

### 2. Aging and Age-Related Diseases

Research indicates that alterations in DNA methylation patterns, including in genes such as DNMT3B, are associated with aging and the epigenetic clock. Specifically:

- **Aging**: Age-related changes in DNMT3B activity may contribute to global hypomethylation observed in many tissues, which is a hallmark of cellular aging.
- **Age-Related Diseases**: Aberrant DNA methylation, including alterations in DNMT3B expression, has been implicated in various age-related diseases, including neurodegenerative diseases (e.g., Alzheimer’s disease), cancer, and others. For instance, decreased DNMT3B activity may be associated with genomic instability often seen in cancerous tissues.

### 3. Drug Interactions

Several drugs and drug classes that target DNA methylation may interact with DNMT3B:

- **Azacitidine (Vidaza)**: A nucleoside analog that inhibits DNA methyltransferases, including DNMT3B, and is used to treat certain hematological malignancies.
- **Decitabine (Dacogen)**: Another drug that inactivates DNMTs, leading to demethylation and reactivation of silenced genes in cancer.

Research is ongoing into additional compounds that may modulate DNMT3B activity, particularly in cancer therapies.

### 4. Pathways and Biological Processes

DNMT3B is involved in various biological pathways and processes:

- **DNA Methylation**: Critical for establishing de novo methylation patterns across the genome during early development.
- **Regulation of Gene Expression**: Participates in gene silencing and transcriptional repression, influencing a variety of downstream targets.
- **Embryonic Development**: Essential for proper development and cellular differentiation.
- **Immunodeficiency-Centromeric Instability-Facial Anomalies Syndrome (ICF Syndrome)**: Mutations in DNMT3B are causative for this syndromic condition, which manifests as immunological deficits and developmental anomalies.
- **Histone Modification**: DNMT3B interacts with histone-modifying complexes, affecting chromatin structure and gene accessibility.

### Conclusion

DNMT3B is a vital gene that plays a multifaceted role in epigenetic regulation and cellular processes relevant to development, aging, and disease. Its interactions with other proteins and pathways underscore its importance in maintaining genomic integrity and regulating gene expression.