CLONING OF THE MULTICOPY SUPPRESSOR GENE SUR7 - EVIDENCE FOR A FUNCTIONAL-RELATIONSHIP BETWEEN THE YEAST ACTIN-BINDING PROTEIN RVS167 AND APUTATIVE MEMBRANOUS PROTEIN

The rvs161 and rvs167 mutant cells exhibit several identical phenotype s including sensitivity to several different growth conditions and mor phological defects such as alteration of the actin cytoskeleton and bu dding patterns. The selection of genes that, when overexpressed, are a ble to suppress the reduced viability upon carbon starvation of the rv s167 mutant strain, has allowed the cloning of the SUR7 gene (Accessio n Number Z46729x11). We showed that the suppressive ability of the ove rexpressed SUR7 gene concerns all the rvs167 phenotypes. However, this suppression is only partial since the rvs167-suppressed strain is not of wild-type phenotype. Moreover, SUR7 is also able to suppress parti ally the phenotypes exhibited by the rvs161 and rvs167 rvs161 mutant s trains. The SUR7 gene encodes a putative integral membrane protein wit h four transmembrane domains. Furthermore, sequence comparisons reveal ed that Sur7p and two other proteins, Yn1194p and Yd1222p, present sig nificant sequence and structural similarities. Taken together, these r esults strongly suggest that the Rvs161 and Rvs167 proteins act togeth er in relation with Sur7p. Moreover, the putative transmembranous char acter of Sur7p suggests a membrane localization of the Rvs function, a localization which is consistent with the different rvs phenotypes an d the actin-Rvs167p interaction. (C) 1997 by John Wiley & Sons, Ltd.