CSTF1 (cleavage stimulation factor subunit 1) is a core component of the mammalian polyadenylation machinery required for pre-mRNA 3' end cleavage and processing 1. As part of the cleavage stimulation factor complex, CSTF1 facilitates interaction between polyadenylation factors to form stable RNA processing complexes on pre-mRNA substrates 1. CSTF1 associates with other polyadenylation machinery including CPSF and integrator complex components during transcription of snRNA genes 2. In disease contexts, CSTF1 dysregulation has emerging relevance to neurodegeneration and cancer. CSTF1 was identified as a neuroprotective candidate gene in Alzheimer disease (AD) models, where reversing its aberrant downregulation rescued behavioral impairments in Drosophila expressing tau pathology 3. Peripheral CSTF1 expression is significantly elevated in late-onset AD patients compared to healthy controls 4. Additionally, genetic variation in CSTF1 associates with breast cancer risk in BRCA2 mutation carriers 5, and CSTF1 participates in cell-mediated immunity regulation within competing endogenous RNA networks in abdominal aortic aneurysm 6. CSTF1 also functions downstream of p53 in DNA damage response pathways, where p53 inhibits mRNA 3' processing through direct interaction with CSTF1 and BARD1 7.