NUDT21 belongs to the Nudix hydrolase family of pyrophosphatases. NUDT21 localizes to the paraspeckles and forms a heterodimer with CPSF6 or CPSF7 to comprise the CFIm(mammalian cleavage factor I) complex. NUDT21 being the smaller subunit of the complex, is present in all heterodimer combinations. NUDT21 has a vital role in pre-mRNA 3’ cleavage and polyadenylation processing.