Enlargement of the endoplasmic reticulum membrane in Saccharomyces cerevisiae is not necessarily linked to the unfolded protein response via Ire1p

Conditions that stress the endoplasmic reticulum (ER) in Saccharomyces cere visiae can elicit a combination of an unfolded protein response (UPR) and a n inositol response (TR), This results in increased synthesis of ER protein -folding factors and of enzymes participating in phospholipid biosynthesis. It was suggested that in cells grown on glucose or galactose medium, the U PR and the IR are linked and controlled bg the ER stress sensor Ire1p. Howe ver, our studies suggest that during growth on oleate the IR is controlled both bg an Ire1p-dependent pathway and by an Ire1p-independent pathway. (C) 1999 Federation of European Biochemical Societies.