title: Rkr1/Ltn1 Ubiquitin Ligase-mediated Degradation of Translationally Stalled Endoplasmic Reticulum Proteins.
abstract: Aberrant nonstop proteins arise from translation of mRNA molecules beyond the coding sequence into the 3'-untranslated region. If a stop codon is not encountered, translation continues into the poly(A) tail, resulting in C-terminal appendage of a polylysine tract and a terminally stalled ribosome. In Saccharomyces cerevisiae, the ubiquitin ligase Rkr1/Ltn1 has been implicated in the proteasomal degradation of soluble cytosolic nonstop and translationally stalled proteins. Rkr1 is essential for cellular fitness under conditions associated with increased prevalence of nonstop proteins. Mutation of the mammalian homolog causes significant neurological pathology, suggesting broad physiological significance of ribosome-associated quality control. It is not known whether and how soluble or transmembrane nonstop and translationally stalled proteins targeted to the endoplasmic reticulum (ER) are detected and degraded. We generated and characterized model soluble and transmembrane ER-targeted nonstop and translationally stalled proteins. We found that these proteins are indeed subject to proteasomal degradation. We tested three candidate ubiquitin ligases (Rkr1 and ER-associated Doa10 and Hrd1) for roles in regulating abundance of these proteins. Our results indicate that Rkr1 plays the primary role in targeting the tested model ER-targeted nonstop and translationally stalled proteins for degradation. These data expand the catalog of Rkr1 substrates and highlight a previously unappreciated role for this ubiquitin ligase at the ER membrane.
authors.affiliation: From the Department of Biology, Ball State University, Muncie, Indiana 47306 and.
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Crowder
authors.affiliation: the Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Geigges
authors.affiliation: From the Department of Biology, Ball State University, Muncie, Indiana 47306 and.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Gibson
authors.affiliation: From the Department of Biology, Ball State University, Muncie, Indiana 47306 and.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Fults
authors.affiliation: From the Department of Biology, Ball State University, Muncie, Indiana 47306 and.
authors.forename: Bryce W
authors.initials: BW
authors.lastname: Buchanan
authors.affiliation: the Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Sachs
authors.affiliation: the Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Schink
authors.affiliation: the Department of Biology, University of Konstanz, 78457 Konstanz, Germany stefan.kreft@uni-konstanz.de.
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Kreft
authors.affiliation: From the Department of Biology, Ball State University, Muncie, Indiana 47306 and emrubenstein@bsu.edu.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Rubenstein
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D060746:Endoplasmic Reticulum-Associated Degradation / Q000235:genetics*; D014176:Protein Biosynthesis; D059748:Proteolysis; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C519403:Rkr1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases
keywords: E3 ubiquitin ligase; ER quality control; Saccharomyces cerevisiae; endoplasmic reticulum-associated protein degradation (ERAD); protein translocation; ribosome; ribosome-associated degradation; translation; yeast genetics