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Báo cáo khóa học: SUT2 is a novel multicopy suppressor of low activity of the cAMP/protein kinase A pathway in yeast

SUT2was found ina screen formulticopy suppressorsof the synthetic slow growth phenotype of aDras2Dgpa2double deletion mutant. It failed, however, to cure the lethal phenotype of aDras1Dras2mutant suggesting that it acts upstreamof Ras or in a parallel pathway. By testing cAMP-dependent reactions including the accumulation of storage carbohydrates, pseudohyphal differentiation, entry of mei-osis as well as the measurement ofFLO11reporter activity we show that Sut2pmodulates the activity of protein kinase A (PKA) | Eur. J. Biochem. 271 1284-1291 2004 FEBS 2004 doi 10.1111 j.l432-1033.2004.04034.x SUT2 is a novel multicopy suppressor of low activity of the cAMP protein kinase A pathway in yeast Michael Rutzler Andre Reissaus Magdalena Budzowska and Wolfhard Bandlow Ludwig-Maximilians-Universitat MUnchen Department Biologie I Bereich Genetik Munich Germany SUT2 was found in a screen for multicopy suppressors of the synthetic slow growth phenotype of a Dras2 Dgpa2 double deletion mutant. It failed however to cure the lethal phenotype of a Dras1 Dras2 mutant suggesting that it acts upstream of Ras or in a parallel pathway. By testing cAMPdependent reactions including the accumulation of storage carbohydrates pseudohyphal differentiation entry of mei-osis as well as the measurement of FLO11 reporter activity we show that Sut2p modulates the activity of protein kinase A PKA . Additionally we demonstrate that cellular levels of Ras2p are affected by Sut2p and that Sut2-GFPp accumulates significantly in the nucleus. Based on the observed influence of high SUT2 gene dosage on PKA activity as well as Sut2p s homology to the presumptive transcription factor Sut-p we suggest that Sut2p contributes to regulation of PKA activity at the level of transcription. Keywords Saccharomyces cerevisiae cAMP PKA pathway suppressors genetic screen. In the yeast Saccharomyces cerevisiae two distinct GTP-binding G protein systems have been found to activate adenylate cyclase a The Ras proteins Ras-p and Ras2p - which are members of the highly conserved family of small GTP-binding proteins and b the Gpr-p Gpa2p carbohydrate receptor system consisting of the G protein coupled receptor GPCR Gpr-p and its coupled heterotrimeric G protein composed of Gpa2 Ga 2 and the atypical Gp and Gy subunits Gpb-p Gpb2p and Gpg-p respectively 3 4 . rasl ras2 Double mutants are not viable indicating a specific role of the Ras proteins that cannot be complemented by Gpa2p whereas Dgpa2 Dras2 mutants display a very slow .