Mapping regions in Ste5 that support Msn5-dependent and -independent nuclear export

Careful control of the available pool of the MAPK scaffold Ste5 is important for mating pathway activation and prevention of inappropriate mating differentiation in haploid S. cerevisiae. Ste5 shuttles constitutively through the nucleus where it is degraded by a ubiquitin-dependent mechanism triggered by G1 CDK phosphorylation. Here we narrow down regions of Ste5 that mediate nuclear export. Four regions in Ste5 relocalize SV40-TAgNLS-GFP-GFP from nucleus to cytoplasm. One region is N-terminal, dependent on exportin Msn5/Ste21/Kap142, and interacts with Msn5 in two hybrid assays independently of mating pheromone, Fus3, Kss1, Ptc1, the NLS/PM, and RING-H2. A second region overlaps the PH domain and Ste11 binding site and two others are on the vWA domain and include residues essential for MAPK activation. We find no evidence for dependence on Crm1/Xpo1 despite numerous potential nuclear export sequences (NESs) detected by LocNES and NETNES1.1 predictors. Thus, Msn5 (homolog of human Exportin-5) and one or more exportins or adapter molecules besides Crm1/Xpo1 may regulate Ste5 through multiple recognition sites.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author