Genetic evidence far interactions between yeast importin alpha (Srp1p) andits nuclear export receptor, Cse1p

The yeast Srp1p protein functions as an import receptor for proteins bearin g basic nuclear localization signals. Cse1p, the yeast homolog of mammalian GAS, recycles Srp1p back to the cytoplasm after import substrates have bee n released into the nucleoplasm. In this report we describe genetic interac tions between SRP1 and CSE1. Results from genetic suppression and synthetic lethality studies demonstrate that these gene products interact to ensure accurate chromosome segregation. We also describe new mutant alleles of CSE 1 and analyze a new temperature-sensitive allele of CSE1, cse1-2. This alle le causes high levels of chromosome missegregation and cell cycle arrest du ring mitosis at the nonpermissive temperature.