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The role of tmRNA nucleotides and the SmpB protein in setting the translational frame on tmRNA
Author(s) -
Watts Talina,
Healey David,
Jones DeAnna,
Buskirk Allen
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.224
Subject(s) - open reading frame , ribosome , ef tu , biology , transfer rna , translation (biology) , messenger rna , mutant , genetics , rna , biochemistry , microbiology and biotechnology , peptide sequence , gene
tmRNA rescues ribosomes that are stalled on defective mRNA templates in eubacteria. Together with its protein partner SmpB, tmRNA mimics a tRNA by entering ribosomes and linking an alanine residue to the growing polypeptide chain. The ribosome then abandons the defective mRNA template and resumes translation on tmRNA, adding ten additional amino acids to the nascent polypeptide. As a result of tmRNA action, stalled ribosomes are released and recycled and the aborted protein product is tagged for destruction by proteases. How does the ribosome choose the right position on tmRNA to resume translation? Previous studies implicate the sequence UAGUC found immediately upstream of the first codon in the tmRNA open reading frame. These nucleotides are highly conserved in natural tmRNA sequences. Mutations cause loss of function and improper frame choice. Using a genetic selection that ties the life of E. coli cells to the function of tmRNA, we have identified several SmpB mutants that rescue an inactive tmRNA in which this upstream sequence has been altered. This links SmpB to the function of these key tmRNA nucleotides. We show that our SmpB mutants affect frame choice using an in vivo assay for tagging in the various frames. We conclude that SmpB plays a role in setting the reading frame on tmRNA. This work was supported by Grant GM77633 from the National Institutes of Health.