title: Specificity in endoplasmic reticulum-stress signaling in yeast entails a step-wise engagement of HAC1 mRNA to clusters of the stress sensor Ire1.
abstract: Insufficient protein-folding capacity in the endoplasmic reticulum (ER) induces the unfolded protein response (UPR). In the ER lumen, accumulation of unfolded proteins activates the transmembrane ER-stress sensor Ire1 and drives its oligomerization. In the cytosol, Ire1 recruits HAC1 mRNA, mediating its non-conventional splicing. The spliced mRNA is translated into Hac1, the key transcription activator of UPR target genes that mitigate ER-stress. In this study, we report that oligomeric assembly of the ER-lumenal domain is sufficient to drive Ire1 clustering. Clustering facilitates Ire1's cytosolic oligomeric assembly and HAC1 mRNA docking onto a positively charged motif in Ire1's cytosolic linker domain that tethers the kinase/RNase to the transmembrane domain. By the use of a synthetic bypass, we demonstrate that mRNA docking per se is a pre-requisite for initiating Ire1's RNase activity and, hence, splicing. We posit that such step-wise engagement between Ire1 and its mRNA substrate contributes to selectivity and efficiency in UPR signaling.
authors.affiliation: Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Eelco
authors.initials: E
authors.lastname: van Anken
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: David
authors.initials: D
authors.lastname: Pincus
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States.
authors.forename: Scott
authors.initials: S
authors.lastname: Coyle
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Tomás
authors.initials: T
authors.lastname: Aragón
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Christof
authors.initials: C
authors.lastname: Osman
authors.affiliation: Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Lari
authors.affiliation: Department of Gene Therapy and Gene Regulation, Center for Applied Medical Research, Pamplona, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Gómez Puerta
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Korennykh
authors.affiliation: Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism; D016000:Cluster Analysis; D017124:Conserved Sequence; D003600:Cytosol / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D056811:Unfolded Protein Response
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; C091341:HAC1 protein, S cerevisiae; D008562:Membrane Glycoproteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D001120:Arginine; C082863:IRE1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases
keywords: S. cerevisiae; biochemistry; cell biology; endoplasmic reticulum; mRNA processing; mRNA targeting; stress signaling; unfolded protein response