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 .
The yeast Clp1 is a subunit of cleavage factor IA (CF IA) and is involved in mRNA cleavage and polyadenylation [PUBMED:22216186]. Clp1 also mediates interactions between CF IA and another complex of the yeast mRNA cleavage and polyadenylation machinery, the Cleavage-Polyadenylation Factor (CPF) [PUBMED:21993299]. It seems that human Clp1 and yeast Clp1 are not functional orthologues [PUBMED:18648070]. Human Clp1, and its archeal homologue [PUBMED:19299550], but not yeast Clp1, are 5'-OH polynucleotide kinases. In humans Clp1 functions as a RNA kinase important in tRNA splicing [PUBMED:18648070, PUBMED:24766809], and is also implicated in mRNA and siRNA maturation [PUBMED:15109492, PUBMED:17495927, PUBMED:17786051].