Yeast Proteomics

The carboxy-terminal domain (CTD) of the largest sub-
unit of RNA polymerase II is phosphorylated soon after
transcriptional initiation.We have shown that the essential FCP1 gene of S. cerevisiae is linked genetically to RNApolymerase II and encodes a CTD phosphatase essential for dephosphorylation of RNA polymerase II in vivo. Fcp1p contains a phosphatase motif, CCC
DXDX(T/V)CC, which is novel for eukaryotic protein
phosphatases and essential for Fcp1p to function in
vivo. This motif is also required for recombinant Fcp1p
to dephosphorylate the RNA polymerase II CTD or
the artificial substrate p-nitrophenylphosphate in vitro.
The effects of fcp1 mutations in global run-on and
genome-wide expression studies show that transcription
tion by RNA polymerase II in S. cerevisiae generally
requires CTD phosphatase.