The Saccharomyces cerevisiae RanGTP-binding protein Msn5p is involved in different signal transduction pathways

In eukaryotes, control of transcription by extracellular signals involves t he translocation to the nucleus of at least one component of the signal tra nsduction pathway. Transport through the nuclear envelope requires the acti vity of an import or export receptor that interacts with the small GTPase R an. We have cloned the MSN5 gene of the yeast Saccharomyces cerevisiae that is postulated to encode one of these receptors. Msn5p belongs to a family of proteins with a conserved N-terminal sequence that acts as a RanGTP-bind ing domain. The results presented here provide genetic data supporting Msn5 p involvement in several different signal transduction pathways.;All of the se pathways include changes in gene expression, and regulated nucleocytopla smic redistribution of a component in response to external conditions has a lready been described in some of them. We have cloned MSN5 following two di fferent strategies. Msn5p was constitutively localized in die nucleus. Phen otypic analysis of the msn5 mutant demonstrated that this protein participa tes in processes such as carabolite repression, calcium signaling, mating, and cell proliferation, as well as being involved in previously characteriz ed phosphate utilization. Therefore, Msn5p could be a receptor for several proteins involved in different signaling pathways.