title: Induction of intranuclear membranes by overproduction of Opi1p and Scs2p, regulators for yeast phospholipid biosynthesis, suggests a mechanism for Opi1p nuclear translocation.
abstract: In the yeast Saccharomyces cerevisiae, the expression of phospholipid biosynthetic genes is suppressed by the Opi1p negative regulator. Opi1p enters into the nucleoplasm from the nuclear membrane to suppress the gene expression under repressing conditions. The binding of Opi1p to the nuclear membrane requires an integral membrane protein, Scs2p and phosphatidic acid (PA). Although it is demonstrated that the association of Opi1p with membranes is affected by PA levels, how Opi1p dissociates from Scs2p is unknown. Here, we found that fluorescently labelled Opi1p accumulated on a perinuclear region in an Scs2p-dependent manner. Electron microscopic analyses indicated that the perinuclear region consists of intranuclear membranes, which may be formed by the invagination of the nuclear membrane due to the accumulation of Opi1p and Scs2p in a restricted area. As expected, localization of Opi1p and Scs2p in the intranuclear membranes was detected by immunoelectron microscopy. Biochemical analysis showed that Opi1p recovered in the membrane fraction was detergent insoluble while Scs2p was soluble, implying that Opi1p behaves differently from Scs2p in the fraction. We hypothesize that Opi1p dissociates from Scs2p after targeting to the nuclear membrane, making it possible to be released from the membrane quickly when PA levels decrease.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Masuda
authors.affiliation: Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Oshima
authors.affiliation: Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan.
authors.forename: Tetsuko
authors.initials: T
authors.lastname: Noguchi
authors.affiliation: Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan kagiwada@cc.nara-wu.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kagiwada
mesh_terms: D021581:Active Transport, Cell Nucleus; D008565:Membrane Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D009685:Nuclear Envelope / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; C096105:OPI1 protein, S cerevisiae; D010712:Phosphatidic Acids; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C501314:Scs2 protein, S cerevisiae
keywords: Saccharomyces cerevisiae; endoplasmic reticulum; gene expression; nuclear membrane; phospholipid