Control of cell division by nutrients, and ER stress signaling in Saccharomyces cerevisiae

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Title: Control of cell division by nutrients, and ER stress signaling in Saccharomyces cerevisiae
Author: Guo, Jinbai
Abstract: Cell cycle progression of Saccharomyces cerevisiae cells was monitored in continuous cultures limited for glucose or nitrogen . The G1 cell cycle phase , before initiation of DNA replication , did not exclusively expand when growth rate decreased . Especially during nitrogen limitation , non -G1 phases expanded almost as much as G1 . In addition , cell size remained constant as a function of growth rate . These results contrast with current views that growth requirements are met before initiation of DNA replication , and suggest that distinct nutrient limitations differentially impinge on cell cycle progression . Therefore , multiple mechanisms are hypothesized to regulate the coordination of cell growth and cell division . Genetic interactions were identified between the dose -dependent cell -cycle regulator 2 (DCR2 ) phosphatase and genes involving in secretion /unfolded protein response pathway , including IRE1 , through a genome -wide dominant negative genetic approach . Accumulation of unfolded proteins in the endoplasmic reticulum triggers the unfolded protein response (UPR ) . How the UPR is downregulated is not well understood . Inositol requirement 1 (IRE1 ) is an endoplasmic reticulum transmembrane UPR sensor in Saccharomyces cerevisiae . When the UPR is triggered , Ire1p is autophosphorylated , on Ser 840 and Ser 841 , inducing the cytosolic endonuclease activity of Ire1p , thereby initiating the splicing and translational de -repression of HAC1 mRNA . Homologous to Atf /Creb1 (Hac1p ) activates UPR transcription . We found that that Dcr2p phosphatase functionally and physically interacts with Ire1p . Overexpression of DCR2 , but not of a catalytically inactive DCR2 allele , significantly delays HAC1 splicing and sensitizes cells to the UPR . Furthermore , Dcr2p physically interacts in vivo with Ire1p -S840E , S841E , which mimics phosphorylated Ire1p , and Dcr2p dephosphorylates Ire1p in vitro . Our results are consistent with de -phosphorylation of Ire1p being a mechanism for antagonizing UPR signaling .
URI: http : / /hdl .handle .net /1969 .1 /5912
Date: 2007-09-17

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Control of cell division by nutrients, and ER stress signaling in Saccharomyces cerevisiae. Available electronically from http : / /hdl .handle .net /1969 .1 /5912 .

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