ATXN1 (ataxin 1) is a chr6-binding factor that functions as a transcriptional corepressor in Notch signaling pathways. It acts as a CBF1 corepressor to suppress Notch-mediated transcription in the absence of Notch intracellular domain, binding to promoters like HEY and potentially assisting NCOR2 and RBPJ in transcriptional repression 1. ATXN1 also binds RNA in vitro and may participate in RNA metabolism, though its precise role remains incompletely defined. The protein is involved in brain development in concert with CIC and ATXN1L. Pathologically, ATXN1 is most notably associated with spinocerebellar ataxia type 1 (SCA1), a dominantly inherited neurodegenerative disease caused by CAG repeat expansion. Expanded ATXN1 causes dysfunctional calcium signaling in human motor neurons and alters critical transcriptional programs 2. Even subtle variations in wild-type ATXN1 expression levels contribute to ataxia, highlighting ATXN1 as a dosage-sensitive gene requiring precise transcriptional and posttranscriptional regulation, including miRNA-mediated control of 5' UTR sequences 3. ATXN1 variants are also detected in sporadic amyotrophic lateral sclerosis as risk factors 4, and ATXN1 is implicated as a cancer stemness gene in metastatic prostate cancer 5.