CSTF1, also known as cleavage stimulation factor subunit 1, is involved in the polyadenylation and 3'end cleavage of pre-mRNAs. Similar to mammalian G protein beta subunits, this protein contains transducin-like repeats. Several transcript variants with different 5' UTR, but encoding the same protein, have been found for this gene. Recombinant human CSTF1 protein, fused to His-tag at C-terminus, was expressed in E.coli.