Identification of a Novel Guanine Nucleotide Exchange Factor for the Rho GTPase*
- Matthew J. Hart‡,
- Sanju Sharma,
- Nadia elMasry,
- Rong-Guo Qiu,
- Peter McCabe,
- Paul Polakis and
- Gideon Bollag
- ‡ To whom correspondence should be addressed: ONYX Pharmaceuticals, 3031 Research Dr., Richmond, CA 94806. Tel.: 510-262-8781; E-mail: matt{at}onyx-pharm.com
Abstract
The Rho GTPase promotes proliferation and cytoskeletal rearrangements in mammalian cells. To understand the regulation of Rho, it is important to characterize guanine nucleotide exchange factors (GEFs), which stimulate the dissociation of GDP and subsequent binding of GTP. Using Rho as an affinity ligand, we have isolated a 115-kDa protein (p115-RhoGEF) that binds specifically to the nucleotide-depleted state. A full-length cDNA encoding p115-RhoGEF was isolated, and its protein product, which exhibited sequence homology to Dbl and Lbc, catalyzed the exchange of GDP for GTP specifically on Rho and not on the Rac, Cdc42, or Ras GTPases. p115-RhoGEF is capable of regulating cell proliferation, as determined by its ability to induce the transformation of NIH 3T3 cells. Northern and Western analysis suggests that p115-RhoGEF is ubiquitously expressed. These results indicate that p115-RhoGEF may be a general regulator of Rho and its associated cellular phenotypes.
Footnotes
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↵* 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) U64105[GenBank].
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↵1 The abbreviations used are:
- GAP
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GTPase-activating protein
- GEF
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guanine nucleotide exchange factor
- GTPγS
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guanosine 5′-3-O-(thio)triphosphate
- kb
-
kilobase pair(s)
- DH
-
Dbl homology
- PH
-
pleckstrin homology
- PAGE
-
polyacrylamide gel electrophoresis.
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- Received May 23, 1996.
- Revision received July 19, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
