Role of phosphatidylcholine (PC) turnover products in regulation of the INO1 gene: Sec14 homologues study.
Roman Holic (1), Peter Griac (1)
(1) Bioenergetics, Animal Bioch. and Genetics, Moyzesova 61, Ivanka pri Dunaji, 900 28, Slovakia
Transcription of yeast phospholipid biosynthesis structural genes containing UASINO responds to the availability of soluble precursors inositol and choline, and to the changes of phospholipid metabolism. The INO1 gene is deregulated (derepressed when inositol was present) under the conditions of increased PC turnover, as occurs in the sec14delta cki1delta strain (Sec14p represents major yeast phosphatidylinositol transfer protein, Cki1p choline kinase of the CDP-choline pathway). Five proteins (Sfhp) share primary sequence homology with Sec14p. Two of them, Sfh2p and Sfh4p, when overexpressed, complemented very well the otherwise essential Sec14p requirement in growth and secretion. In this work we were interested, if Sec14 homologues are able to correct the deregulation of INO1 caused by missing Sec14p. Our results show that (i) none of the Sec14 homologues was able to substitute for Sec14p in its regulatory aspects toward phospholipid biosynthesis, (ii) removal of phospholipase D activity (Pld1) corrected the INO1 regulation in yeast strains with otherwise high PC turnover and resulting deregulation of the INO1 gene, (iii) increased steady-state PA levels corresponded with derepressed levels of the INO1 gene. Overall, our results support the model, that excess PA leads to derepression of the INO1 gene (Henry and Patton-Vogt, Prog. Nucleic Acid Res. Mol. Biol. 61 (1998) 133-79). This study was supported by VEGA 2/4130/4 and APVT (Slovak republic) 51-016502 grants.
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