title: Translation initiation region sequence preferences in Escherichia coli.
abstract: BACKGROUND
  The mRNA translation initiation region (TIR) comprises the initiator codon, Shine-Dalgarno (SD) sequence and translational enhancers. Probably the most abundant class of enhancers contains A/U-rich sequences. We have tested the influence of SD sequence length and the presence of enhancers on the efficiency of translation initiation.
  
  
  RESULTS
  We found that during bacterial growth at 37 degrees C, a six-nucleotide SD (AGGAGG) is more efficient than shorter or longer sequences. The A/U-rich enhancer contributes strongly to the efficiency of initiation, having the greatest stimulatory effect in the exponential growth phase of the bacteria. The SD sequences and the A/U-rich enhancer stimulate translation co-operatively: strong SDs are stimulated by the enhancer much more than weak SDs. The bacterial growth rate does not have a major influence on the TIR selection pattern. On the other hand, temperature affects the TIR preference pattern: shorter SD sequences are preferred at lower growth temperatures. We also performed an in silico analysis of the TIRs in all E. coli mRNAs. The base pairing potential of the SD sequences does not correlate with the codon adaptation index, which is used as an estimate of gene expression level.
  
  
  CONCLUSIONS
  In E. coli the SD selection preferences are influenced by the growth temperature and not influenced by the growth rate. The A/U rich enhancers stimulate translation considerably by acting co-operatively with the SD sequences.
authors.affiliation: Institute of Technology, University of Tartu, Nooruse 1, Tartu 50411, Estonia. riboloom@hot.ee
authors.forename: Vladimir
authors.initials: V
authors.lastname: Vimberg
authors.forename: Age
authors.initials: A
authors.lastname: Tats
authors.forename: Maido
authors.initials: M
authors.lastname: Remm
authors.forename: Tanel
authors.initials: T
authors.lastname: Tenson
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D018387:Codon, Initiator; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017930:Genes, Reporter; D010442:Peptide Chain Initiation, Translational; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D038621:Regulatory Sequences, Ribonucleic Acid / Q000235:genetics*; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D018387:Codon, Initiator; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D038621:Regulatory Sequences, Ribonucleic Acid