An unexpected binding mode for a Pol II CTD peptide phosphorylated at Ser7 in the active site of the CTD phosphatase Ssu72
Abstract
Ssu72, an RNA polymerase II C-terminal domain (CTD) phospho-Ser5 (pSer5) phosphatase, was recently reported to have pSer7 phosphatase activity as well. We report here the crystal structure of a ternary complex of the N-terminal domain of human symplekin, human Ssu72, and a 10-mer pSer7 CTD peptide. Surprisingly, the peptide is bound in the Ssu72 active site with its backbone running in the opposite direction compared with a pSer5 peptide. The pSer7 phosphatase activity of Ssu72 is ∼4000-fold lower than its pSer5 phosphatase activity toward a peptide substrate, consistent with the structural observations.
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↵1 Corresponding author
E-mail ltong{at}columbia.edu
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Supplemental material is available for this article.
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Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.198853.112.
- Received June 18, 2012.
- Accepted August 28, 2012.
- Copyright © 2012 by Cold Spring Harbor Laboratory Press