Alternative polyadenylation modulates gene expresion via changing the length of 3'UTR. Among the complexes involving in APA, CFIm complex plays a central role in determining the usage of proximal PAS versus distal one. NUDT21, also named as CFIm25 and CPSF5, is the core component of CFIm complex. To date, except CPSF6 and CPSF7, there are few proteins reported to interact with NUDT21. In this project, the interactome of NUDT21 was identified by IP-MS.