FCP1, the RAP74-Interacting Subunit of a Human Protein Phosphatase That Dephosphorylates the Carboxyl-terminal Domain of RNA Polymerase IIO

doi:10.1074/jbc.273.42.27593

FCP1, the RAP74-Interacting Subunit of a Human Protein Phosphatase That Dephosphorylates the Carboxyl-terminal Domain of RNA Polymerase IIO*

From the ^‡Banting and Best Department of Medical Research and ^**Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada M5G 1L6, the ^‖Department of Genetics, Research Institute, the Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8, and the ^¶Section of Molecular and Cellular Biology, Division of Biological Sciences, University of California, Davis, California 95616

Abstract

TFIIF (RAP30/74) is a general initiation factor that also increases the rate of elongation by RNA polymerase II. A two-hybrid screen for RAP74-interacting proteins produced cDNAs encoding FCP1a, a novel, ubiquitously expressed human protein that interacts with the carboxyl-terminal evolutionarily conserved domain of RAP74. Related cDNAs encoding FCP1b lack a carboxyl-terminal RAP74-binding domain of FCP1a. FCP1 is an essential subunit of a RAP74-stimulated phosphatase that processively dephosphorylates the carboxyl-terminal domain of the largest RNA polymerase II subunit. FCP1 is also a stoichiometric component of a human RNA polymerase II holoenzyme complex.

Footnotes

↵* This work was supported in part by grants (to J. G.) from the Medical Research Council of Canada and the National Cancer Institute of Canada with funds from the Canadian Cancer Society and by National Institutes of Health Grant GM-33300 (to M. E. D.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF081287.
↵§ Supported by a fellowship from the Medical Research Council of Canada.
↵‡ Medical Research Council of Canada Distinguished Scientist and International Research Scholar of the Howard Hughes Medical Institute. To whom correspondence should be addressed: Banting and Best Dept. of Medical Research and Dept. of Molecular and Medical Genetics, University of Toronto, 112 College St., Toronto, Ontario, Canada M5G 1L6. Tel.: 416-978-4141; Fax: 416-978-8528; E-mail:jack.greenblatt{at}utoronto.ca.
↵2 J. Langlois, M. Kobor, and J. Greenblatt, unpublished data.
↵3 J. Archambault and J. Greenblatt, unpublished data.
Abbreviations:

RNAP

RNA polymerase

TFII

general transcription factor for RNA polymerase II

CTD

carboxyl-terminal domain of the largest subunit of RNA polymerase II

RNAP IIA

unphosphorylated form of RNA polymerase II

RNAP IIO

hyperphosphorylated form of RNA polymerase II

P-TEFb

positive transcription elongation factor

HIV-1

human immunodeficiency virus, type 1

Tat

transactivator protein of HIV-1

RAP

RNA polymerase II associating protein

FCP

TFIIF-associating CTD phosphatase

RACE

rapid amplification of mRNA ends

GST

glutathioneS-transferase

AT

3-aminotriazole

PCR

polymerase chain reaction

ACB

affinity chromatography buffer

CHAPS

3-[(3-cholamidopropyl)dimethylammonio]-1-pro-panesulfonic acid

DBD

DNA-binding domain.
- Received June 26, 1998.
- Revision received August 7, 1998.