Cleavage and polyadenylation specificity factor (CPSF) is a multi-protein complex essential for the cleavage of the 3' end of pre-mRNA and the subsequent addition of a poly(A) tail, a crucial step in mRNA maturation and stability. CPSF recognizes the polyadenylation signal sequence on pre-mRNA and interacts with other factors to ensure precise and efficient processing of mRNA precursors in eukaryotic cells.