The Rsp5 ubiquitin ligase plays a role in many cellular processes including the biosynthesis of unsaturated fatty acids. The PIS1 (phosphatidylinositol synthase gene) encoding the enzyme Pis1p which catalyses the synthesis of phosphatidylinositol from CDP-diacyglycerol and inositol, was isolated in a screen for multicopy suppressors of the rsp5 temperature sensitivity phenotype. Suppression was allele non-specific. Interestingly, expression of PIS1 was 2-fold higher in the rsp5 mutant than in wild-type yeast, whereas the introduction of PIS1 in a multicopy plasmid increased the level of Pis1p 6-fold in both backgrounds. We demonstrate concomitantly that the expression of INO1 (inositol phosphate synthase gene) was also elevated approx. 2-fold in the rsp5 mutant as compared with the wild-type, and that inositol added to the medium improved growth of rsp5 mutants at a restrictive temperature. These results suggest that enhanced phosphatidylinositol synthesis may account for PIS1 suppression of rsp5 defects. Analysis of lipid extracts revealed the accumulation of saturated fatty acids in the rsp5 mutant, as a consequence of the prevention of unsaturated fatty acid synthesis. Overexpression of PIS1 did not correct the cellular fatty acid content; however, saturated fatty acids (C16:0) accumulated preferentially in phosphatidylinositol, and (wild-type)-like fatty acid composition in phosphatidylethanolamine was restored.
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Research Article|
March 15 2006
Enhanced levels of Pis1p (phosphatidylinositol synthase) improve the growth of Saccharomyces cerevisiae cells deficient in Rsp5 ubiquitin ligase
Pawel Kaliszewski;
Pawel Kaliszewski
*Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
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Thierry Ferreira;
Thierry Ferreira
†Laboratoire de Génétique de la Levure, CNRS-UMR6161, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France
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Beata Gajewska;
Beata Gajewska
‡Department of Biochemistry, Faculty of Medicine, Medical University of Warsaw, Banacha 1, 02-097 Warsaw, Poland
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Anna Szkopinska;
Anna Szkopinska
§Department of Lipid Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
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Thierry Berges;
Thierry Berges
†Laboratoire de Génétique de la Levure, CNRS-UMR6161, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France
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Teresa Żołądek
Teresa Żołądek
1
*Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
1To whom correspondence should be addressed (email teresa@ibb.waw.pl).
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Publisher: Portland Press Ltd
Received:
October 25 2005
Revision Received:
December 12 2005
Accepted:
December 20 2005
Accepted Manuscript online:
December 20 2005
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2006
Biochem J (2006) 395 (1): 173–181.
Article history
Received:
October 25 2005
Revision Received:
December 12 2005
Accepted:
December 20 2005
Accepted Manuscript online:
December 20 2005
Citation
Pawel Kaliszewski, Thierry Ferreira, Beata Gajewska, Anna Szkopinska, Thierry Berges, Teresa Żołądek; Enhanced levels of Pis1p (phosphatidylinositol synthase) improve the growth of Saccharomyces cerevisiae cells deficient in Rsp5 ubiquitin ligase. Biochem J 1 April 2006; 395 (1): 173–181. doi: https://doi.org/10.1042/BJ20051726
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