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Molecular and Cellular Biology, February 2007, p. 926-936, Vol. 27, No. 3
0270-7306/07/$08.00+0     doi:10.1128/MCB.01361-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Role for the Ssu72 C-Terminal Domain Phosphatase in RNA Polymerase II Transcription Elongation{triangledown}

Mariela Reyes-Reyes{dagger} and Michael Hampsey*

Department of Biochemistry, Division of Nucleic Acids Enzymology, UMDNJ-Robert Wood Johnson Medical School, 683 Hoes Lane West, Piscataway, New Jersey 08854

Received 25 July 2006/ Returned for modification 18 August 2006/ Accepted 1 November 2006

The RNA polymerase II (RNAP II) transcription cycle is accompanied by changes in the phosphorylation status of the C-terminal domain (CTD), a reiterated heptapeptide sequence (Y1S2P3T4S5P6S7) present at the C terminus of the largest RNAP II subunit. One of the enzymes involved in this process is Ssu72, a CTD phosphatase with specificity for serine-5-P. Here we report that the ssu72-2-encoded Ssu72-R129A protein is catalytically impaired in vitro and that the ssu72-2 mutant accumulates the serine-5-P form of RNAP II in vivo. An in vitro transcription system derived from the ssu72-2 mutant exhibits impaired elongation efficiency. Mutations in RPB1 and RPB2, the genes encoding the two largest subunits of RNAP II, were identified as suppressors of ssu72-2. The rpb1-1001 suppressor encodes an R1281A replacement, whereas rpb2-1001 encodes an R983G replacement. This information led us to identify the previously defined rpb2-4 and rpb2-10 alleles, which encode catalytically slow forms of RNAP II, as additional suppressors of ssu72-2. Furthermore, deletion of SPT4, which encodes a subunit of the Spt4-Spt5 early elongation complex, also suppresses ssu72-2, whereas the spt5-242 allele is suppressed by rpb2-1001. These results define Ssu72 as a transcription elongation factor. We propose a model in which Ssu72 catalyzes serine-5-P dephosphorylation subsequent to addition of the 7-methylguanosine cap on pre-mRNA in a manner that facilitates the RNAP II transition into the elongation stage of the transcription cycle.

* Corresponding author. Mailing address: Department of Biochemistry, Robert Wood Johnson Medical School, 683 Hoes Lane West, Piscataway, NJ 08854. Phone: (732) 235-5888. Fax: (732) 235-5889. E-mail: michael.hampsey{at}umdnj.edu.

{triangledown} Published ahead of print on 13 November 2006.

{dagger} Present address: Advaxis, Inc., Princeton, NJ 08540.

Molecular and Cellular Biology, February 2007, p. 926-936, Vol. 27, No. 3
0270-7306/07/$08.00+0     doi:10.1128/MCB.01361-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Mikhaylova, O., Ignacak, M. L., Barankiewicz, T. J., Harbaugh, S. V., Yi, Y., Maxwell, P. H., Schneider, M., Van Geyte, K., Carmeliet, P., Revelo, M. P., Wyder, M., Greis, K. D., Meller, J., Czyzyk-Krzeska, M. F. (2008). The von Hippel-Lindau Tumor Suppressor Protein and Egl-9-Type Proline Hydroxylases Regulate the Large Subunit of RNA Polymerase II in Response to Oxidative Stress. Mol. Cell. Biol. 28: 2701-2717 [Abstract] [Full Text]  
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