This family consists of several pre-mRNA cleavage complex II Clp1 (or HeaB) proteins. Six different protein factors are required in vitro for 3' end formation of mammalian pre-mRNAs by endonucleolytic cleavage and polyadenylation. Clp1 is a subunit of cleavage complex IIA, which is required for cleavage, but not for polyadenylation of pre-mRNA [1].

1: Human pre-mRNA cleavage factor II(m) contains homologs of yeast proteins and bridges two other cleavage factors. de Vries H, Ruegsegger U, Hubner W, Friedlein A, Langen H, Keller W; EMBO J 2000;19:5895-5904. PMID:11060040