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Structural mapping of Rtg2p determinants involved in retrograde signaling and aging of Saccharomyces cerevisiae


Cells of the baker´s yeast Saccharomyces cerevisiae can adapt their metabolism in response to the physiological state of their mitochondria by activating the nuclear transcription, an interorganelle communication known as retrograde signaling. This signaling is controlled by the transcription factor complex Rtg1p-Rtg3p. When mitochondrial activity is high the complex is sequestered in the cytoplasm, whereas in cells with dysfunctional mitochondria, the complex migrates to the nucleus to activate the transcription of several genes involved in the production of a-ketoglutarate, the precursor of glutamate. Rtg2p is a positive modulator of such system because, after binding the negative factor Mks1p, allows translocation of the Rtg1/3p complex from the cytoplasm to the nucleus. Although Rtg2p i) is a homologue of exopolyphosphatases, ii) contains a N-terminal domain important for its function and iii) participates in the mechanism of yeast replicative and chronologic aging, there is no detailed structural map of this protein to date. The goal of this project is to identify structural determinants in Rtg2p, involved in retrograde signaling and in aging of S. cerevisiae. This will be achieved by resecting Rtg2p protein and by point mutation site-directed mutagenesis, obtained by rational design based on analysis of coevolved amino acid communities. The function of the mutant proteins will be analyzed both in retrograde signaling response and in yeast replicative aging. The results of this work would shed light to mitochondrial functions involved in aging process, programmed cell death and neurodegenerative diseases caused by mitochondrial deficiency. (AU)