The function of Ensembl gene identifier ENSG00000101138 (CSTF1, cleavage stimulation factor subunit 1) is as follows. One of the multiple factors required for polyadenylation and 3'-end cleavage of mammalian pre-mRNAs (PubMed:10669729). May be responsible for the interaction of CSTF with other factors to form a stable complex on the pre-mRNA (PubMed:10669729). .