Divergent tRNA-like element supports initiation, elongation, and termination of protein biosynthesis.

Abstract

The cricket paralysis virus internal ribosome entry site (IRES) can, in the absence of canonical initiation factors and initiator tRNA (Met-tRNAi), occupy the ribosomal P-site and assemble 80S ribosomes. Here we show that the IRES assembles mRNA-80S ribosome complexes by recruitment of 60S subunits to preformed IRES-40S complexes. Addition of eukaryotic elongation factors eEF1A and eEF2 and aminoacylated elongator tRNAs resulted in the synthesis of peptides, implying that the IRES RNA itself mimics the function of Met-tRNAi in the P-site to trigger the first translocation step without peptide bond formation. IRES-80S complexes that contained a stop codon in the A-site recruited eukaryotic release factor eRF1, resulting in ribosome rearrangements in a surprisingly eEF2-dependent manner. Thus, this P-site-occupying IRES directs the assembly of 80S ribosomes, sets the translational reading frame, and mimics the functions of both Met-tRNAi and peptidyl tRNA to support elongation and termination.

• Authors: Eric Jan, Terri Goss Kinzy, Peter Sarnow
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 100 Issue 26 Pg. 15410-5 (Dec 23 2003) ISSN: 0027-8424 [Print] United States
• PMID: 14673072 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Codon, Terminator
• Peptides
• RNA, Transfer, Amino Acyl
• RNA, Transfer
• Luciferases

Topics

• Amino Acid Sequence
• Base Sequence
• Codon, Terminator (genetics)
• Genes, Reporter
• Luciferases (genetics)
• Peptide Chain Elongation, Translational
• Peptide Chain Initiation, Translational
• Peptide Chain Termination, Translational
• Peptides (chemistry, metabolism)
• Protein Biosynthesis
• RNA, Transfer (genetics, metabolism)
• RNA, Transfer, Amino Acyl (genetics, metabolism)
• Ribosomes (chemistry, metabolism)
• Transcription, Genetic