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 biological roles are yet to be determined. A temperature‐sensitive sly1 mutant arrests the vesicular transport from the ER to Golgi compartments at 37°C. We screened for multicopy suppressor genes that restore the colony formation of the sly1 ts mutant to discover functionally interacting components. The suppressor genes obtained were classified as: (1) those that encode a multifunctional suppressor, SSD1 ; (2) heat shock proteins, SSB1 and SSB2 ; (3) cell surface proteins, WSC1 , WSC2 and MID2 ; (4) ER–Golgi transport proteins, USO1 and BET1 ; and (5) an as‐yet‐uncharacterized protein, HSD1 ( h igh‐copy suppressor of S LY1 d efect 1 ). By epitope tagging of the gene product, we found that Hsd1 protein is an ER‐resident membrane protein. Its overproduction induced enlargement of ER‐like membrane structures. Copyright © 2001 John Wiley & Sons, Ltd.