The highly conserved and essential protein Ssu72 has intrinsic phosphatase activity and plays an essential role in the transcription cycle. Ssu72 was originally identified in a yeast genetic screen as enhancer of a defect caused by a mutation in the transcription initiation factor TFIIB. It binds to TFIIB and is also involved in mRNA elongation. Ssu72 is further involved in both poly(A) dependent and independent termination. It is a subunit of the yeast cleavage and polyadenylation factor (CPF), which is part of the machinery for mRNA 3'-end formation. Ssu72 is also essential for transcription termination of snRNAs.