In vivo evidence for the prokaryotic model of extended codon-anticodon interaction in translation initiation.
Initiation codon context is an important determinant of translation initiation rates in both prokaryotes and eukaryotes. Such sequences include the Shine- Dalgarno ribosome-binding site, as well as other motifs surrounding the initiation codon. One proposed interaction is between the base immediately preceding the initiation codon (-1 position) and the nucleotide 3' to the tRNAf(Met) anticodon, at position 37. Adenine is conserved at position 37, and a uridine at -1 has been shown in vitro to favor initiation. We have tested this model in vivo, by manipulating the chloroplast of the green alga Chlamydomonas reinhardtii, where the translational machinery is prokaryotic in nature. We show that translational defects imparted by mutations at the petA -1 position can be suppressed by compensatory mutations at position 37 of an ectopically expressed tRNA(fMet). The mutant tRNAs are fully aminoacylated and do not interfere with the translation of other proteins. Although this extended base pairing is not an absolute requirement for initiation, it may convey added specificity to transcripts carrying non-standard initiation codons, and/or preserve translational fidelity under certain stress conditions.
Esposito
Donna
D
Boyce Thompson Institute for Plant Research and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
Fey
Julien P
JP
Eberhard
Stephan
S
Hicks
Amanda J
AJ
Stern
David B
DB
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000926:Anticodon / Q000235:genetics*; D020029:Base Pairing; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics*; D003062:Codon / Q000235:genetics*; D003580:Cytochromes / Q000378:metabolism; D045348:Cytochromes f; D009154:Mutation; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism
D020418:Algal Proteins; D000926:Anticodon; D003062:Codon; D003580:Cytochromes; D015800:Protozoan Proteins; D012333:RNA, Messenger; D012343:RNA, Transfer; D045348:Cytochromes f