A mutation in the effector region of Ras2 can be partially suppressed by alteration of a 'nonessential' region of Ras.
Phenotypically normal revertants of budding yeast cells that contain the hyperactive RAS2Val19 allele often result from second-site mutations within the RAS2 locus itself. Several such intragenic revertants harboring a suppressed RAS2Val19 allele as their only RAS gene were analyzed. All such suppressors resulted from single amino acid substitutions that affected either: (i) the effector region of Ras2, (ii) the C-terminal CAAX box of Ras2, or (iii) residues known to be critical for GTP binding in Ras proteins. While these suppressor mutations completely suppressed the hyperactive phenotype induced by the Val19 substitution, they did not block the ability of Ras2 to promote growth at normal temperatures. These results suggest that in yeast, attenuation of Ras proteins can effectively block hyperactive phenotypes without completely blocking the growth-promoting function. A spontaneous intragenic mutation that restored function to an effector mutant was mapped to a 'nonessential' region of Ras proteins. Based on this genetic interaction with the effector region and the report that deletions of this region affect Ras/GAP interaction, we suggest that this region may have a functional role in Ras activation of target effectors.
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Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854.
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D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D019204:GTP-Binding Proteins / Q000235:genetics*; D005800:Genes, Fungal; D016153:Genes, Suppressor; D011905:Genes, ras; D006150:Guanine Nucleotides / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011499:Protein Processing, Post-Translational; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D014633:Valine / Q000737:chemistry; D018631:ras Proteins
D017931:DNA Primers; D005656:Fungal Proteins; D006150:Guanine Nucleotides; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); C489015:RAS2 protein, S cerevisiae; D018631:ras Proteins; D014633:Valine