The ARPC4 gene, which encodes the p20 subunit of the Arp2/3 complex, plays crucial roles in actin dynamics, cell motility, and nuclear functions. Here’s a detailed breakdown addressing your inquiries:

### 1. Associated Genes
Besides the known association with the tubulin tyrosine ligase-like family, member 3 (TTLL3) due to read-through transcription, ARPC4 is also associated with genes involved in cytoskeletal dynamics and cellular signaling. Some notable genes include:
   - **ARPC1A, ARPC1B, ARP2, ARP3**: Other subunits of the Arp2/3 complex.
   - **WAS/WASL**: Wiskott-Aldrich syndrome protein family members that regulate actin polymerization and are often involved in immune responses.
   - **NAN**: This gene encodes a nucleic acid binding protein that may interact with components of the Arp2/3 complex.

### 2. Aging and Age-Related Diseases
Although direct evidence linking ARPC4 with aging or specific age-related diseases is limited, the role of the Arp2/3 complex in cellular motility and maintenance of cytoskeletal integrity indirectly suggests potential associations. Impairment in actin dynamics has been linked to:
   - **Neurodegenerative Diseases**: Changes in actin dynamics may influence neuronal function and contribute to diseases such as Alzheimer’s.
   - **Cancer**: Alterations in the Arp2/3 complex impact cell migration and invasion, which are key in tumor progression.
   - **Muscle Atrophy**: Dysfunction of the cytoskeleton can lead to the loss of muscle mass often seen in aging.

### 3. Drug Interactions
There are currently no specific drugs that are directly known to target ARPC4. However, drugs that affect the actin cytoskeleton or have broader effects on cellular dynamics may modulate the activity of the Arp2/3 complex. Some classes of drugs that may indirectly impact the function of ARPC4 include:
   - **Cytoskeletal Inhibitors**: Such as cytochalasins and latrunculin that disrupt actin polymerization.
   - **Chemotherapeutic Agents**: That induce cytotoxicity may affect actin dynamics and, consequently, Arp2/3 activity.
   - **Small-molecule inhibitors**: Some compounds targeting nucleation-promoting factors may affect the Arp2/3 complex activity indirectly.

### 4. Pathways and Biological Processes
ARPC4 is involved in several biological processes and pathways, including:
   - **Actin Cytoskeleton Dynamics**: Essential for the formation of branched actin networks.
   - **Cell Motility**: Mediated by the polymerization of actin filaments which drives cellular movement.
   - **Nuclear Function**: ARPC4 is involved in nuclear actin polymerization, impacting processes like gene transcription, DNA damage repair, and homologous recombination.
   - **Signal Transduction Pathways**: It is often part of pathways involving growth factor signaling that stimulates actin remodeling.
   - **Endocytosis**: Assists in the cellular uptake of molecules via actin-driven membrane invagination.

In summary, the ARPC4 gene is integral to the coordination of cytoskeletal architecture and cellular processes, with implications in both normal physiology and disease states. While certain connections to aging and pharmacological targeting necessitate further investigation, its role in actin dynamics and nuclear processes underpinned by the Arp2/3 complex illustrates its biological significance.