The Saccharomyces cerevisiae SDC25 C-domain gene product overcomes the dominant inhibitory activity of Ha-Ras Asn-17.
The carboxy-terminal part of the Saccharomyces cerevisiae SDC25 gene product (SDC25 C domain) can elicit activation of mammalian Ras proteins. Specifically, SDC25 C domain functions as an exchange factor for cellular Ras proteins in CHO cells. In this study, we used the dominant inhibitory Ha-Ras Asn-17 mutant and SDC25 C domain to further investigate the interaction between cellular Ras proteins and their putative endogenous guanine nucleotide-releasing factors. Transcription from the polyomavirus thymidine kinase gene (Py tk) promoter is strongly inhibited by the expression of Ha-Ras Asn-17 in NIH 3T3 cells. Coexpression of SDC25 C domain overcomes the negative effect of the Ras mutant on the Py tk promoter. On the other hand, transactivation of the Ras-responsive element of the Py tk promoter induced by SDC25 C domain is lost upon coexpression of increasing amounts of Ha-Ras Asn-17. In addition, coexpression of SDC25 C domain overcomes the inhibition of proliferation of NIH 3T3 cells caused by Ha-Ras Asn-17. These results are consistent with the idea that the Ha-Ras Asn-17 mutant functions by titrating an upstream activator of cellular Ras proteins.
Dana-Farber Cancer Institute, Boston, Massachusetts.
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F
Schweighoffer
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Cai
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Chevallier-Multon
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I
Fath
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Cooper
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Tocque
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division; D004742:Enhancer Elements, Genetic; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D011905:Genes, ras; D006150:Guanine Nucleotides / Q000378:metabolism; D051379:Mice; D011120:Polyomavirus / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D014162:Transfection; D020668:rap GTP-Binding Proteins
D005656:Fungal Proteins; D006150:Guanine Nucleotides; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D020668:rap GTP-Binding Proteins