SNAPC3 is a subunit of the snRNA-activating protein complex (SNAPc), which regulates transcription of small nuclear RNAs by both RNA polymerase II and III 1. As part of SNAPc, SNAPC3 functions in recognizing and binding to the proximal sequence element (PSE), a basal promoter element shared between these two gene classes, and assists in recruiting essential transcription factors like TBP and BRF2 to snRNA promoters 2. SNAPC3 interacts with other SNAPc subunits, including SNAPC1, to form a functional transcription complex; proper SUMOylation of SNAPC1 is necessary for SNAPc complex assembly and basal snRNA transcription 2. Beyond its canonical role in snRNA transcription, SNAPC3 has emerging clinical relevance in metabolic and oncologic diseases. Genome-wide association studies identified SNAPC3 as a gene linking genetic variation at obesity-risk loci to biological mechanisms affecting body mass index, with associations generalized across multiple tissues including liver and adipose tissue 3. DNA methylation variations at the SNAPC3 locus mediate associations between exclusive breastfeeding and early-life growth trajectories, suggesting a role in developmental programming of obesity risk 4. In osteosarcoma, low SNAPC3 abundance correlates with higher disease-free survival 5, while SNAPC3 has been identified as a novel fusion partner for KMT2A in acute myeloid leukemia 6.