title: Defining the specificity of cotranslationally acting chaperones by systematic analysis of mRNAs associated with ribosome-nascent chain complexes.
abstract: Polypeptides exiting the ribosome must fold and assemble in the crowded environment of the cell. Chaperones and other protein homeostasis factors interact with newly translated polypeptides to facilitate their folding and correct localization. Despite the extensive efforts, little is known about the specificity of the chaperones and other factors that bind nascent polypeptides. To address this question we present an approach that systematically identifies cotranslational chaperone substrates through the mRNAs associated with ribosome-nascent chain-chaperone complexes. We here focused on two Saccharomyces cerevisiae chaperones: the Signal Recognition Particle (SRP), which acts cotranslationally to target proteins to the ER, and the Nascent chain Associated Complex (NAC), whose function has been elusive. Our results provide new insights into SRP selectivity and reveal that NAC is a general cotranslational chaperone. We found surprising differential substrate specificity for the three subunits of NAC, which appear to recognize distinct features within nascent chains. Our results also revealed a partial overlap between the sets of nascent polypeptides that interact with NAC and SRP, respectively, and showed that NAC modulates SRP specificity and fidelity in vivo. These findings give us new insight into the dynamic interplay of chaperones acting on nascent chains. The strategy we used should be generally applicable to mapping the specificity, interplay, and dynamics of the cotranslational protein homeostasis network.
authors.affiliation: Department of Biology and BioX Program, Stanford University, Stanford, California, United States of America.
authors.forename: Marta
authors.initials: M
authors.lastname: del Alamo
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hogan
authors.forename: Sebastian
authors.initials: S
authors.lastname: Pechmann
authors.forename: Veronique
authors.initials: V
authors.lastname: Albanese
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Brown
authors.forename: Judith
authors.initials: J
authors.lastname: Frydman
mesh_terms: D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016681:Genome, Fungal; D023281:Genomics / Q000379:methods*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011485:Protein Binding; D014176:Protein Biosynthesis; D017510:Protein Folding; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D005656:Fungal Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D018271:Signal Recognition Particle; C096099:nascent-polypeptide-associated complex