engleski

The yeast protein Xtc1 functions as a direct transcriptional repressor

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. This same protein has been also implicated to function in mitochondrial DNA maintenance, presumably by being involved in repair of oxidative damage to the mitochondrial genome. We have further analyzed the function of Xtc1 in transcriptional regulation and demonstrate that, when fused to the heterologous DNA binding domain of Gal4, Xtc1 can directly repress transcription of a reporter gene in yeast cells. The repression domain maps to a fragment between amino acids 75 and 100, and interestingly, the C-terminal 126 amino acids bear a weak activation domain. We have also studied the localization of Xtc1 in yeast cells, using an Xtc1 fusion to the green fluorescence protein (GFP) and showed that GFP-Xtc1 localizes to both the nucleus and mitochondria consistent with Xtc1 having a function in both cellular compartments.

yeast; transcription; repression; Xtc1

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