### HDAC3 Gene Overview

**Gene Symbol**: HDAC3  
**Location**: Chromosome 12 in humans (12q21.1)  
**Gene Type**: Protein-coding gene

#### 1. Associated Genes:
In addition to YY1, NCOR1, RARA, and others mentioned in the summaries, HDAC3 is also associated with the following:

- **NCOR2** (Nuclear Receptor Corepressor 2): Works alongside HDAC3 in transcriptional repression.
- **SIRT1 (Sirtuin 1)**: Known to have antagonistic effects on HDAC3, contributing to the regulation of cellular processes involved in aging.
- **KDM6A** (Lysine Demethylase 6A): Involved in the epigenetic regulation together with HDAC3, particularly in the context of cancer.
- **CREB** (cAMP Response Element-Binding Protein): Potential epigenetic interactions in memory and learning processes.

#### 2. Aging and Age-Related Diseases:

- **Role in Aging**: HDAC3 plays a significant role in the regulation of gene expression during aging by influencing chromatin structure, maintaining cellular homeostasis, and regulating cellular senescence.
  
- **Age-Related Diseases**: Aberrant expression or dysfunction of HDAC3 has been linked to several age-related conditions, including:
  - **Neurodegenerative Diseases**: Altered HDAC activity is implicated in Alzheimer's and other neurodegenerative disorders.
  - **Cancer**: Given its potential as a tumor suppressor, dysregulation of HDAC3 is linked to various cancers, including breast and colon cancer.
  - **Metabolic Disorders**: Impacts on lipid metabolism linked to metabolic syndrome and obesity has also been observed.

#### 3. Known Drug Interactions:
HDAC3 is a target for several drug classes that interact with histone deacetylases, including:

- **HDAC Inhibitors**: 
  - **Vorinostat (SAHA)**: An FDA-approved drug for cutaneous T-cell lymphoma that inhibits multiple HDACs, including HDAC3.
  - **Romidepsin**: Another HDAC inhibitor approved for the treatment of peripheral T-cell lymphoma, also affecting HDAC3.
  - **TSA (Trichostatin A)**: A potent HDAC inhibitor often used in research settings to study HDAC function.

- **Other Therapeutic Agents**: There are ongoing studies into small-molecule inhibitors and natural compounds like resveratrol that modulate HDAC activity and potentially influence age-related pathways.

#### 4. Pathways and Biological Processes:

HDAC3 is involved in several critical biological pathways, including:

- **Epigenetic Regulation**: Regulation of gene expression through histone deacetylation and interaction with transcription factors.
- **Cell Cycle Regulation**: Influences the progression and checkpoint control of the cell cycle, impacting cell division and growth.
- **Differentiation and Development**: Plays a role in embryonic development and cellular differentiation processes.
- **Signal Transduction**: Modulates various signaling pathways, including those involving nuclear hormone receptors and other transcription factors.
- **Circadian Rhythm Regulation**: Involved in the control of circadian clock genes and associated processes, such as sleep-wake cycles.

### Summary
The HDAC3 gene encodes an essential histone deacetylase with broad implications in transcriptional regulation, cellular metabolism, and responses to stress. Its interactions with other proteins, associations with aging, and potential as a therapeutic target make it a significant focus in both basic research and clinical studies related to cancer and age-related diseases.