Structure and mechanism of RNA polymerase II CTD phosphatases.
Recycling of RNA polymerase II (Pol II) after transcription requires dephosphorylation of the polymerase C-terminal domain (CTD) by the phosphatase Fcp1. We report the X-ray structure of the small CTD phosphatase Scp1, which is homologous to the Fcp1 catalytic domain. The structure shows a core fold and an active center similar to those of phosphotransferases and phosphohydrolases that solely share a DXDX(V/T) signature motif with Fcp1/Scp1. We demonstrate that the first aspartate in the signature motif undergoes metal-assisted phosphorylation during catalysis, resulting in a phosphoaspartate intermediate that was structurally mimicked with the inhibitor beryllofluoride. Specificity may result from CTD binding to a conserved hydrophobic pocket between the active site and an insertion domain that is unique to Fcp1/Scp1. Fcp1 specificity may additionally arise from phosphatase recruitment near the CTD via the Pol II subcomplex Rpb4/7, which is shown to be required for binding of Fcp1 to the polymerase in vitro.
Department of Chemistry and Biochemistry, Gene Center, University of Munich, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
Tomislav
T
Kamenski
Susanna
S
Heilmeier
Anton
A
Meinhart
Patrick
P
Cramer
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism
D009687:Nuclear Proteins; D012319:RNA Polymerase II; C413483:CTDSP1 protein, human; D010749:Phosphoprotein Phosphatases; C116022:carboxy-terminal domain phosphatase