Multicopy suppressors of the sly1 temperature-sensitive mutation in the ER-Golgi vesicular transport in Saccharomyces cerevisiae

Saccharomyces cerevisiae Sly1 protein is a member of the Sec1/Munc18-family proteins, which are essential for vesicular trafficking, but their exact b iological roles are yet to be determined. A temperature-sensitive sly1 muta nt arrests the vesicular transport from the ER to Golgi compartments at 37 degrees. We screened for multicopy suppressor genes that restore the colony formation of the sly1(ts) mutant to discover functionally interacting comp onents. The suppressor genes obtained were classified as: (1) those that en code a multifunctional suppressor, SSD1; (2) heat shock proteins, SSB1 and SSB2; (3) cell surface proteins, WSC1, WSC2 and MID2; (4) ER-Golgi transpor t proteins, USO1 and BET1; and (5) an as-yet-uncharacterized protein, HSD1 (high-copy suppressor of SLY1 defect 1). By epitope tagging of the gene pro duct, we found that Hsd1 protein is an ER-resident membrane protein. Its ov erproduction induced enlargement of ER-like membrane structures. Copyright (C) 2001 John Wiley & Sons, Ltd.