PMID- 29666249
OWN - NLM
STAT- MEDLINE
DCOM- 20180815
LR  - 20181114
IS  - 1091-6490 (Electronic)
IS  - 0027-8424 (Print)
IS  - 0027-8424 (Linking)
VI  - 115
IP  - 18
DP  - 2018 May 1
TI  - eIF1 Loop 2 interactions with Met-tRNA(i) control the accuracy of start codon 
      selection by the scanning preinitiation complex.
PG  - E4159-E4168
LID - 10.1073/pnas.1800938115 [doi]
AB  - The eukaryotic 43S preinitiation complex (PIC), bearing initiator methionyl 
      transfer RNA (Met-tRNA(i)) in a ternary complex (TC) with eukaryotic initiation 
      factor 2 (eIF2)-GTP, scans the mRNA leader for an AUG codon in favorable context. 
      AUG recognition evokes rearrangement from an open PIC conformation with TC in a 
      "P(OUT)" state to a closed conformation with TC more tightly bound in a "P(IN)" 
      state. eIF1 binds to the 40S subunit and exerts a dual role of enhancing TC 
      binding to the open PIC conformation while antagonizing the P(IN) state, 
      necessitating eIF1 dissociation for start codon selection. Structures of 
      reconstituted PICs reveal juxtaposition of eIF1 Loop 2 with the Met-tRNA(i) D 
      loop in the P(IN) state and predict a distortion of Loop 2 from its conformation 
      in the open complex to avoid a clash with Met-tRNA(i) We show that Ala 
      substitutions in Loop 2 increase initiation at both near-cognate UUG codons and 
      AUG codons in poor context. Consistently, the D71A-M74A double substitution 
      stabilizes TC binding to 48S PICs reconstituted with mRNA harboring a UUG start 
      codon, without affecting eIF1 affinity for 40S subunits. Relatively stronger 
      effects were conferred by arginine substitutions; and no Loop 2 substitutions 
      perturbed the rate of TC loading on scanning 40S subunits in vivo. Thus, Loop 2-D 
      loop interactions specifically impede Met-tRNA(i) accommodation in the P(IN) 
      state without influencing the P(OUT) mode of TC binding; and Arg substitutions 
      convert the Loop 2-tRNA(i) clash to an electrostatic attraction that stabilizes 
      P(IN) and enhances selection of poor start codons in vivo.
FAU - Thakur, Anil
AU  - Thakur A
AD  - Eunice Kennedy Shriver National Institute of Child Health and Human Development, 
      NIH, Bethesda, MD 20892.
FAU - Hinnebusch, Alan G
AU  - Hinnebusch AG
AUID- ORCID: 0000-0002-1627-8395
AD  - Eunice Kennedy Shriver National Institute of Child Health and Human Development, 
      NIH, Bethesda, MD 20892 ahinnebusch@nih.gov.
LA  - eng
PT  - Journal Article
PT  - Research Support, N.I.H., Intramural
DEP - 20180416
PL  - United States
TA  - Proc Natl Acad Sci U S A
JT  - Proceedings of the National Academy of Sciences of the United States of America
JID - 7505876
RN  - 0 (Codon, Initiator)
RN  - 0 (Eukaryotic Initiation Factor-1)
RN  - 0 (RNA, Fungal)
RN  - 0 (RNA, Transfer, Met)
RN  - 0 (Saccharomyces cerevisiae Proteins)
SB  - IM
MH  - Codon, Initiator/*chemistry/genetics/metabolism
MH  - Eukaryotic Initiation Factor-1/*chemistry/genetics/metabolism
MH  - *Nucleic Acid Conformation
MH  - *Peptide Chain Initiation, Translational
MH  - Protein Structure, Secondary
MH  - RNA, Fungal/*chemistry/genetics/metabolism
MH  - RNA, Transfer, Met/*chemistry/genetics
MH  - Ribosome Subunits, Small, Eukaryotic/chemistry/genetics/metabolism
MH  - Saccharomyces cerevisiae/*chemistry/genetics/metabolism
MH  - Saccharomyces cerevisiae Proteins/*chemistry/genetics/metabolism
PMC - PMC5939108
OTO - NOTNLM
OT  - eIF1
OT  - initiation
OT  - ribosome
OT  - translation
OT  - yeast
COIS- The authors declare no conflict of interest.
EDAT- 2018/04/19 06:00
MHDA- 2018/08/16 06:00
PMCR- 2018/11/01
CRDT- 2018/04/19 06:00
PHST- 2018/04/19 06:00 [pubmed]
PHST- 2018/08/16 06:00 [medline]
PHST- 2018/04/19 06:00 [entrez]
PHST- 2018/11/01 00:00 [pmc-release]
AID - 1800938115 [pii]
AID - 201800938 [pii]
AID - 10.1073/pnas.1800938115 [doi]
PST - ppublish
SO  - Proc Natl Acad Sci U S A. 2018 May 1;115(18):E4159-E4168. doi: 
      10.1073/pnas.1800938115. Epub 2018 Apr 16.