Component of the cleavage factor Im (CFIm) complex that functions as an activator of the pre-mRNA 3'-end cleavage and polyadenylation processing required for the maturation of pre-mRNA into functional mRNAs. CFIm contributes to the recruitment of multiprotein complexes on specific sequences on the pre-mRNA 3'-end, so called cleavage and polyadenylation signals (pA signals). Most pre-mRNAs contain multiple pA signals, resulting in alternative cleavage and polyadenylation (APA) producing mRNAs with variable 3'-end formation. The CFIm complex acts as a key regulator of cleavage and polyadenylation site choice during APA through its binding to 5'-UGUA-3' elements localized in the 3'-untranslated region (UTR) for a huge number of pre-mRNAs. CPSF6 enhances NUDT21/CPSF5 binding to 5'-UGUA-3' elements localized upstream of pA signals and promotes RNA looping, and hence activates directly the mRNA 3'-processing machinery. Plays a role in mRNA export. Component of the cleavage factor Im (CFIm) complex which is a heterotetramer composed of two subunits of NUDT21/CPSF5 and two subunits of CPSF6 or CPSF7 or a heterodimer of CPSF6 and CPSF7. The cleavage factor Im (CFIm) complex associates with the CPSF and CSTF complexes to promote the assembly of the core mRNA 3'-processing machinery. Associates with the exon junction complex (EJC). Associates with the 80S ribosome particle. Interacts (via the RRM domain) with NUDT21/CPSF5; this interaction is direct and enhances binding to RNA. Interacts (via Arg/Ser-rich domain) with FIP1L1 (preferentially via unphosphorylated form and Arg/Glu/Asp-rich domain); this interaction mediates, at least in part, the interaction between the CFIm and CPSF complexes and may be inhibited by CPSF6 hyper-phosphorylation. Interacts (via N-terminus) with NXF1; this interaction is direct. Interacts with SRSF3. Interacts with SRSF7. Interacts with SNRNP70. Interacts with TRA2B/SFRS10. Interacts with UPF1. Interacts with UPF3B. Interacts with VIRMA. Interacts (via Arg/Ser-rich domain) with TNPO3; promoting nuclear import of CPSF6 independently of its phosphorylation status (By similarity). Interacts with YTHDC1 (By similarity). Shuttles between the nucleus and the cytoplasm in a transcription- and XPO1/CRM1-independent manner, most probably in complex with the cleavage factor Im complex (CFIm). Colocalizes with PSPC1 in punctate subnuclear structures often located adjacent to nuclear speckles, called paraspeckles, and corresponding to interchromatin granules-associated zones (IGAZs). Distribution in speckles and paraspeckles varies during the cell cycle. Associates at sites of active transcription on nascent perichromatin fibrils (PFs) and perichromatin granules. Nuclear import is mediated via interaction with TNPO3 independently of CPSF6 phosphorylation status. Contains an Arg/Ser-rich domain composed of arginine-serine dipeptide repeats within the C-terminal region that is necessary and sufficient for activating mRNA 3'-processing and alternative polyadenylation (APA). Phosphorylated. Phosphorylated in the Arg/Ser-rich domain by SRPK1, in vitro. Symmetrically dimethylated on arginine residues in the GAR motif by PRMT5 in a WDR77- and CLNS1A-dependent manner. Asymmetrically dimethylated on arginine residues in the GAR motif by PRMT1. Belongs to the RRM CPSF6/7 family.