Molecular cloning of cDNAs encoding a guanine-nucleotide-releasing factor for Ras p21.
The stimulation of a variety of cell surface receptors promotes the accumulation of the active, GTP-bound form of Ras proteins in cells. This is a critical step in signal transduction because inhibition of Ras activation by anti-Ras antibodies or dominant inhibitory Ras mutants blocks many of the effects of these receptors on cellular function. To reach the active GTP-bound state, Ras proteins must first release bound GDP. This rate-limiting step in GTP binding is thought to be catalysed by a guanine-nucleotide-releasing factor (GRF). Here we report the cloning of complementary DNAs from a rat brain library that encode a approximately 140K GRF for Ras p21 (p140Ras-GRF). Its carboxy-terminal region is similar to that of CDC25, a GRF for Saccharomyces cerevisiae RAS. This portion of Ras-GRF accelerated the release of GDP from RasH and RasN p21 in vitro, but not from the related RalA, or CDC42Hs GTP-binding proteins. A region in the amino-terminal end of Ras-GRF is similar to both the human breakpoint cluster protein, Bcr, and the dbl oncogene product, a guanine-nucleotide-releasing factor for CDC42Hs. An understanding of Ras-GRF function will enhance our knowledge of the many signal transduction pathways mediated by Ras proteins.
Shou
C
C
Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111.
Farnsworth
C L
CL
Neel
B G
BG
Feig
L A
LA
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D020663:ras Guanine Nucleotide Exchange Factors; D020666:ras-GRF1
D020662:Guanine Nucleotide Exchange Factors; D009838:Oligodeoxyribonucleotides; D011506:Proteins; D011994:Recombinant Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D020666:ras-GRF1; D006153:Guanosine Diphosphate; D012313:RNA; D004247:DNA; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)