CPSF1

Cleavage and polyadenylation specificity factor subunit 1 is a protein that in humans is encoded by the "CPSF1" gene.
In most cases eukaryotic pre-messenger(m)RNA 3 prime ends are processed in two coordinated steps. First there is a site-specific cleavage by an endonuclease and then the addition of a poly(A) tail at the 3 prime end of the 5 prime cleavage product. Cleavage requires four multisubunit complexes, namely cleavage and polyadenylation specificity factor (CPSF), cleavage stimulation factor (CstF), cleavage factors Im and IIm (CFIm and CFIIm), along with a single subunit poly(A)polymerase (PAP). CPSF1 is the largest component of the CPSF complex composed of CPSF1, CPSF2, CPSF3, CPSF4, FIP1L1, Symplekin and WDR33 and located in the nucleus. 