SART1 (spliceosome associated factor 1) is a multifunctional protein with primary roles in pre-mRNA splicing and emerging functions in DNA damage repair and cell cycle regulation. As a component of the U4/U6-U5 tri-snRNP complex, SART1 participates in spliceosome assembly and catalytic steps of mRNA splicing 1. Beyond splicing, SART1 functions as a direct mitosis-specific microtubule-associated protein that localizes to spindle poles to form a unique 'SART1 cap' structure, promoting spindle pole assembly through recruitment of pericentriolar material proteins 2. SART1 also participates in homologous recombination repair of DNA double-strand breaks by promoting DSB end resection in a BRCA1-dependent manner 3. Clinically, SART1 shows significant relevance to viral infections and cancer. SART1 restricts hepatitis B virus replication by suppressing HNF4α expression, which is essential for HBV transcription 4, and baseline SART1 expression correlates with interferon treatment response in chr11 hepatitis B patients 5. In Toxoplasma gondii, SART1 is essential for parasite virulence and host cell invasion through splicing-dependent mechanisms 6. SART1 is upregulated in several cancer types and regulates Mcl1 splicing to control apoptosis in neuroblastoma; targeting SART1 alongside other spliceosome components sensitizes Mcl1-dependent cancers to Bcl2 inhibitors 1. Loss of SART1 function also drives metabolic dysfunction-associated steatohepatitis progression to hepatocellular carcinoma through NF-κB pathway dysregulation 7.