GSP1 and GSP2, genetic suppressors of the prp20-1 mutant in Saccharomyces cerevisiae: GTP-binding proteins involved in the maintenance of nuclear organization.

摘要: The temperature-sensitive mutation prp20-1 of Saccharomyces cerevisiae exhibits a pleiotropic phenotype associated with general failure to maintain proper organization the nucleus. Its mammalian homolog, RCC1, is not only reported be involved in negative control chromosome condensation but also believed assist coupling DNA replication entry into mitosis. Recent studies on Xenopus RCC1 have strongly suggested further role for this protein formation or maintenance machinery. To elucidate nature various components required PRP20 pathway S. cerevisiae, we undertook search multicopy suppressors prp20 thermosensitive mutant. Two genes, GSP1 and GSP2, were identified that encode almost identical polypeptides 219 220 amino acids. Sequence analyses these proteins show them contain ras consensus domains GTP binding metabolism. levels transcript are about 10-fold those GSP2. As RAS2, GSP2 expression carbon source dependency, while does not. an essential gene, cell viability. We GSP1p nuclear, it can bind vitro assay, finally, which activates small ras-like by increasing stability GTP-bound form causes dominant lethal phenotype. believe two gene products may serve regulating activities multicomponent complex.