TAILIEUCHUNG - Báo cáo Y học: Molecular characterization of MRG19 of Saccharomyces cerevisiae Implication in the regulation of galactose and nonfermentable carbon source utilization

We have reportedpreviously thatmultiple copies ofMRG19 suppressGALgenes inawild-typebut not inagal80strainof Saccharomyces cerevisiae. In this report we show that dis-ruption ofMRG19leads to a decrease in GALinduction whenS. cerevisiaeis inducedwith but not with galactose. Disruption ofMRG19in agal3background (this strainshows long-termadaptationphenotype)furtherdelays theGALinduction, supporting the notion that its function is important only under low inducing signals. | Eur. J. Biochem. 269 5840-5850 2002 FEBS 2002 doi Molecular characterization of MRG19 of Saccharomyces cerevisiae Implication in the regulation of galactose and nonfermentable carbon source utilization Firdous A. Khanday Maitreyi Saha and Paike Jayadeva Bhat Laboratory of Molecular Genetics Biotechnology Center Indian Institute of Technology Powai Mumbai India We have reported previously that multiple copies of MRG19 suppress GAL genes in a wild-type but not in a gal80 strain of Saccharomyces cerevisiae. In this report we show that disruption of MRG19 leads to a decrease in GAL induction when S. cerevisiae is induced with but not with galactose. Disruption of MRG19 in a gal3 background this strain shows long-term adaptation phenotype further delays the GAL induction supporting the notion that its function is important only under low inducing signals. As a corollary disruption of MRG19 in a gal80 strain did not decrease the constitutive expression of GAL genes. These results suggest that MRG19 has a role in GAL regulation only when the induction signal is weak. Unlike the effect on GAL gene expression disruption of MRG19 leads to de-repression of CYC1-driven b-galactosidase activity. MRG19 disruptant also showed a twofold increase in the rate of oxygen uptake as compared with the wild-type strain. ADH2 CTA1 DLD1 and CYC7 promoters that are active during non-fermentative growth did not show any de-repression of b-galactosidase activity in the MRG19 disruptant. Western blot analysis indicated that MRG19 is a glucose repressible gene and is expressed in galactose and glycerol plus lactate. Experiments using green fluorescent protein fusion constructs indicate that Mrg19p is localized in the nucleus consistent with the presence of a consensus nuclear localization signal sequence. Based on the above results we propose that Mrg19p is a regulator of galactose and nonfermentable carbon utilization. Keywords carbon metabolism CYC1 .

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