NUDT21-mediated Alternative Polyadenylation of CDK19 Reprograms Cholesterol Biosynthesis to Drive Colorectal Cancer Progression.

Alternative polyadenylation (APA) is critical for shaping transcriptome diversity by generating mRNA isoforms that differ in the length of their 3'untranslated region (3'UTR). APA dysregulation, a defined feature of tumorigenesis, remains poorly understood in colorectal cancer (CRC). Here, CRISPR/Cas9 screening identifies APA regulator NUDT21 as a key driver of CRC progression. NUDT21 is overexpressed in CRC tumors and correlates with poor prognosis in CRC patients. Genetic ablation of NUDT21 impairs CRC cell proliferation and triggers CD8 T cell anti-tumor response through disrupting cholesterol biosynthesis, leading to delayed tumor progression in syngeneic mouse models. Mechanistically, NUDT21 promotes the generation of cyclin-dependent kinase 19 (CDK19) mRNA isoforms with long 3'UTR by directing usage of distal polyadenylation sites. The long 3'UTR facilitates the export of CDK19 transcripts to the cytoplasm and supports their efficient translation, with no impact on their stability. Truncation of the long 3'UTR of Cdk19 recapitulates cholesterol biosynthesis and proliferative impairments, as well as the enhanced anti-tumor CD8 T cell activity observed upon NUDT21 depletion, whereas CDK19 overexpression rescues these phenotypes. The findings establish the NUDT21-CDK19 axis as a central hub integrating APA manner, cholesterol metabolic reprogramming, and immune evasion in CRC, unveiling potential therapeutic opportunities.