title: Distinct roles for release factor 1 and release factor 2 in translational quality control.
abstract: In bacteria, stop codons are recognized by two similar class 1 release factors, release factor 1 (RF1) and release factor 2 (RF2). Normally, during termination, the class 2 release factor 3 (RF3), a GTPase, functions downstream of peptide release where it accelerates the dissociation of RF1/RF2 prior to ribosome recycling. In addition to their canonical function in termination, both classes of release factor are also involved in a post peptidyl transfer quality control (post PT QC) mechanism where the termination factors recognize mismatched (i.e. error-containing) ribosome complexes and promote premature termination. Here, using a well defined in vitro system, we explored the role of release factors in canonical termination and post PT QC. As reported previously, during canonical termination, RF1 and RF2 recognize stop codons in a similar manner, and RF3 accelerates their rate of dissociation. During post PT QC, only RF2 (and not RF1) effectively binds to mismatched ribosome complexes; and whereas the addition of RF3 to RF2 increased its rate of release on mismatched complexes, the addition of RF3 to RF1 inhibited its rate of release but increased the rate of peptidyl-tRNA dissociation. Our data strongly suggest that RF2, in addition to its primary role in peptide release, functions as the principle factor for post PT QC.
authors.affiliation: From the Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Alexandros D
authors.initials: AD
authors.lastname: Petropoulos
authors.affiliation: From the Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Megan E
authors.initials: ME
authors.lastname: McDonald
authors.affiliation: From the Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Rachel
authors.initials: R
authors.lastname: Green
authors.affiliation: the Department of Biology, Washington University in St. Louis, St. Louis, Missouri 63130 hzaher@wustl.edu.
authors.forename: Hani S
authors.initials: HS
authors.lastname: Zaher
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D010443:Peptide Chain Termination, Translational / Q000502:physiology*; D010454:Peptide Termination Factors / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; C489005:prfA protein, E coli; C489006:prfB protein, E coli
keywords: Protein Synthesis; Ribosome; Translation; Translation Control; Translation Release Factor