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 .
(Microbial infection) Binds HIV-1 capsid-nucleocapsid (HIV-1 CA-NC) complexes and might thereby promote the integration of the virus in the nucleus of dividing cells (in vitro).
Subcellular locations: Nucleus, Nucleus, Nucleoplasm, Nucleus speckle, Cytoplasm
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 .