title: Translation initiation factor 2gamma mutant alters start codon selection independent of Met-tRNA binding.
abstract: Selection of the AUG start codon for translation in eukaryotes is governed by codon-anticodon interactions between the initiator Met-tRNA(i)(Met) and the mRNA. Translation initiation factor 2 (eIF2) binds Met-tRNA(i)(Met) to the 40S ribosomal subunit, and previous studies identified Sui(-) mutations in eIF2 that enhanced initiation from a noncanonical UUG codon, presumably by impairing Met-tRNA(i)(Met) binding. Consistently, an eIF2gamma-N135D GTP-binding domain mutation impairs Met-tRNA(i)(Met) binding and causes a Sui(-) phenotype. Intragenic A208V and A382V suppressor mutations restore Met-tRNA(i)(Met) binding affinity and cell growth; however, only A208V suppresses the Sui(-) phenotype associated with the eIF2gamma-N135D mutation. An eIF2gamma-A219T mutation impairs Met-tRNA(i)(Met) binding but unexpectedly enhances the fidelity of initiation, suppressing the Sui(-) phenotype associated with the eIF2gamma-N135D,A382V mutant. Overexpression of eIF1, which is thought to monitor codon-anticodon interactions during translation initiation, likewise suppresses the Sui(-) phenotype of the eIF2gamma mutants. We propose that structural alterations in eIF2gamma subtly alter the conformation of Met-tRNA(i)(Met) on the 40S subunit and thereby affect the fidelity of start codon recognition independent of Met-tRNA(i)(Met) binding affinity.
authors.affiliation: Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Pankaj V
authors.initials: PV
authors.lastname: Alone
authors.forename: Chune
authors.initials: C
authors.lastname: Cao
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dever
mesh_terms: D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D018387:Codon, Initiator / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D018387:Codon, Initiator; D004268:DNA-Binding Proteins; D015852:Eukaryotic Initiation Factor-2; C501391:GCN4 protein, S cerevisiae; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors
references.citation: Science. 2001 Nov 9;294(5545):1299-304
references.pmid: 11701921
references.citation: Genes Dev. 2004 Dec 15;18(24):3078-93
references.pmid: 15601822
references.citation: Mol Cell Biol. 2004 Nov;24(21):9437-55
references.pmid: 15485912
references.citation: J Mol Biol. 2004 Jan 23;335(4):923-36
references.pmid: 14698289
references.citation: Mol Cell. 2005 Oct 28;20(2):251-62
references.pmid: 16246727
references.citation: Arch Microbiol. 1983 Aug;135(1):63-7
references.pmid: 6354131
references.citation: Nature. 1998 Aug 27;394(6696):854-9
references.pmid: 9732867
references.citation: EMBO J. 2002 Apr 2;21(7):1821-32
references.pmid: 11927566
references.citation: Science. 1995 Dec 1;270(5241):1464-72
references.pmid: 7491491
references.citation: Genes Dev. 2003 Nov 15;17(22):2786-97
references.pmid: 14600024
references.citation: Genetics. 1990 Mar;124(3):483-95
references.pmid: 2179049
references.citation: Proc Natl Acad Sci U S A. 1989 Apr;86(8):2784-8
references.pmid: 2649894
references.citation: Mol Cell. 2005 Jan 21;17(2):265-75
references.pmid: 15664195
references.citation: Mol Cell Biol. 2007 Mar;27(5):1677-85
references.pmid: 17189426
references.citation: Mol Cell. 2007 Apr 13;26(1):41-50
references.pmid: 17434125
references.citation: Genes Dev. 1997 Sep 15;11(18):2396-413
references.pmid: 9308967
references.citation: Annu Rev Microbiol. 2005;59:407-50
references.pmid: 16153175
references.citation: Mol Cell Biol. 1992 Jan;12(1):248-60
references.pmid: 1729602
references.citation: EMBO J. 1996 Nov 15;15(22):6311-20
references.pmid: 8947054
references.citation: Cell. 1988 Aug 26;54(5):621-32
references.pmid: 3136928
references.citation: Mol Cell Biol. 2003 Aug;23(15):5431-45
references.pmid: 12861028
references.citation: Proc Natl Acad Sci U S A. 1989 Oct;86(19):7515-9
references.pmid: 2678106
references.citation: J Biol Chem. 2004 Mar 12;279(11):10634-42
references.pmid: 14688270
references.citation: EMBO J. 1995 May 15;14(10):2239-49
references.pmid: 7774582
references.citation: Genes Dev. 2007 May 15;21(10):1217-30
references.pmid: 17504939
references.citation: Annu Rev Biochem. 1997;66:639-78
references.pmid: 9242920
references.citation: J Biol Chem. 2006 May 5;281(18):12636-44
references.pmid: 16522633
references.citation: Proc Natl Acad Sci U S A. 2007 Nov 20;104(47):18445-50
references.pmid: 18000047
references.citation: Structure. 1996 Oct 15;4(10):1141-51
references.pmid: 8939739
references.citation: Mol Cell Biol. 1991 May;11(5):2723-35
references.pmid: 2017175