CPSF1 depletion results in decreased proliferation, enhanced apoptosis, cell cycle redistribution and alternative polyadenylation (APA) events. (A) Western blot analysis of MDA-MB-231 and MDA-MB-468 lysates infected with control and shRNA lentivirus targeting CPSF1. (B) Growth of MDA-MB-231 cells and MDA-MB-468 cells was measured after infection with CPSF1 shRNA lentivirus and control shRNA lentivirus. The results shown are the means ± standard deviation (s.d.) (n = 3). (C) CPSF1 knockdown increased the apoptosis rate in MDA-MB-231 cells (n = 3). (D) CPSF1 depletion led to cell cycle redistribution in MDA-MB-231 (n = 3). (E) Enriched pathways in CPSF1 knockdown MDA-MB-231 cells. (F) Scatterplot of percentage of distal poly(A) site usage index (PDUI) in control and CPSF1 knockdown MDA-MB-231 cells, where mRNAs were significantly shortened (n = 243) and lengthened (n = 336) after CPSF1 knockdown. (G) Correlation between distal poly(A) site usage and gene expression levels of control and CPSF1 knockdown MDA-MB-231 cells. (H) Representative RNA-seq density plots along with ΔPDUI values for genes whose 3′UTR was unchanged (MMS22L), lengthened (SPIDR and MIA3) and shortened (MTA3) in response to CPSF1 knockdown. **p < 0.01, ***p < 0.001. Abbreviations: APA, alternative polyadenylation; PDUI, percentage of distal poly(A) site usage index.