engleski

A novel yeast protein Xtc1 is required for manteinance of mitochondrial functions in Saccharomyces cerevisiae cells

The S. cerevisiae protein Xtc1p was identified as a protein that binds to the activation domains of human E2F-1, the viral activator VP16 and the yeast activator Gal4. It was also shown to copurify with the RNA polymerase II holoenzyme complex and to modulate the response of RNA polymerase II to transcriptional activators. Interestingly, this same protein has also been implicated to function in maintenance of mitochondrial DNA in yeast cells. We have further analyzed the functions of Xtc1 and show that yeast strains deleted for the XTC1 gene are respiratory deficient as demonstrated by their inability to grow on glycerol/ethanol as the sole carbon source. A GFP-Xtc fusion protein localizes to both mitochondrial and nuclear compartments which is consistent with Xtc1p having a function in both. To gain further insight into the nuclear and/or mitochondrial functions of Xtc1p, we have used microarray analysis to compare the whole genome transcription profile of a xtc1� ´ strain to that of a wild type strain, as well as to that of a strain lacking mitochondrial DNA (rho0). Our results show that cells deleted for XTC1 have a transcription profile characteristic of cells with impaired mitochondrial functions. In fact, in both rho0 and xtc1� ´ strains higher level of expression was observed for genes encoding mitochondrial proteins, enzymes of the glycolytic pathway and of the citric acid cycle, cell wall components, membrane transporters and genes normally induced by nutrient deprivation and a variety of stresses. Consistent with the observed induction of genes related to cell stress and those encoding membrane transporters, both rho0 and xtc1� ´ cells show increased resistance to severe heat shock and exhibit a pleiotropic drug resistance phenotype.

yeast; mitochondria; Xtc1; mtDNA

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