The SNU13 gene, also known as SNU13 (also referred to as RNU13), encodes a highly conserved nuclear protein involved in critical cellular processes, including RNA splicing and ribosome biogenesis. Here are detailed insights based on your requests:

### 1. Associated Genes
SNU13 is implicated in various RNA splicing and ribosomal biogenesis pathways and may interact with several other genes and their products. Although many genes may be indirectly associated due to its role in splicing and ribosome assembly, key associated genes include:

- **NHP2**: As mentioned, SNU13 shares sequence similarity with this yeast protein, which is also involved in RNA processing.
- **PRPF8**: A component of the spliceosome involved in pre-mRNA splicing.
- **U4 snRNA**: Particularly important as SNU13 binds to its 5' stem-loop, critical for spliceosome assembly.
- **RRP5**: Part of the ribosome biogenesis pathway.

### 2. Aging and Age-Related Diseases
Research has shown that components of the spliceosome, including SNU13, can have implications in various age-related processes. While specific studies directly linking SNU13 to aging or age-related diseases are limited, defects in RNA processing and ribosome biogenesis are known to contribute to age-related decline in cellular functions. Furthermore, errors in splicing have been associated with age-related diseases such as:

- **Neurodegenerative diseases**: Aberrant splicing is a contributing factor in diseases like Alzheimer's.
- **Cancer**: Misregulation of splicing factors can lead to oncogenesis and tumor progression.

### 3. Known Drug Interactions
There are currently no specific drugs directly targeting or interacting with SNU13 mentioned in readily available literature. However, due to its role in RNA splicing, compounds that modulate splicing mechanisms, such as small-molecule inhibitors or modulating agents of the spliceosome, may have downstream effects that could affect SNU13's functions. For instance:

- **Splicing modulators (e.g., E7107)**: These have been studied for their ability to influence spliceosome activity and may indirectly impact SNU13 function or expression.

### 4. Pathways and Biological Processes
SNU13 is involved in several key biological processes and pathways, including:

- **RNA Splicing**: It is a crucial component of the spliceosome, facilitating the removal of introns from pre-mRNA.
- **Ribosome Biogenesis**: Involved in the assembly and maturation of the small subunit of ribosomes in the nucleolus.
- **Pre-mRNA Processing**: Enhances the computational execution of RNA modifications and rearrangements.
- **U4/U6.U5 Tri-snRNP Complex Formation**: Plays a role in the assembly of spliceosomal complexes essential for splicing efficiency.

In summary, SNU13 is integral to the processing and modification of RNA, influencing ribosome biogenesis and various splicing pathways, which are crucial for maintaining cellular homeostasis and responding to developmental and stress signals. Its roles position it as a significant player in the cellular response to aging and disease processes. Further research could elucidate more about its role in specific diseases and how drug interactions might affect its function.