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- Jin, Haining, et al.
(författare)
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Influences on gene expression in vivo by a Shine-Dalgarno sequence.
- 2006
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Ingår i: Mol Microbiol. - : Wiley. - 0950-382X .- 1365-2958. ; 60:2, s. 480-92
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Shine-Dalgarno (SD+: 5'-AAGGAGG-3') sequence anchors the mRNA by basepairing to the 16S rRNA in the small ribosomal subunit during translation initiation. We have here comparedhow an SD+ sequence influences gene expression, if located upstream or downstream of an initiation codon.The positive effect of an upstream SD+ is confirmed. A downstream SD+ gives decreased gene expression.This effect is also valid for appropriately modified natural Escherichia coli genes. If an SD+ is placedbetween two potential initiation codons, initiation takes place predominantly at the second start site.The first start site is activated if the distance between this site and the downstream SD+ is enlargedand/or if the second start site is weakened. Upstream initiation is eliminated if a stable stem-loopstructure is placed between this SD+ and the upstream start site. The results suggest that the two startsites compete for ribosomes that bind to an SD+ located between them. A minor positive contribution toupstream initiation resulting from 3' to 5' ribosomal diffusion along the mRNA is suggested. Analysisof the E. coli K12 genome suggests that the SD+ or SD-like sequences are systematically avoided in theearly coding region suggesting an evolutionary significance.
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