Mutation Analysis of the 5′ Untranslated Region of the Cold Shock cspA mRNA of Escherichia coli
AUTOR(ES)
Yamanaka, Kunitoshi
FONTE
American Society for Microbiology
RESUMO
The mRNA for CspA, a major cold shock protein in Escherichia coli, contains an unusually long (159 bases) 5′ untranslated region (5′-UTR), and its stability has been shown to play a major role in cold shock induction of CspA. The 5′-UTR of the cspA mRNA has a negative effect on its expression at 37°C but has a positive effect upon cold shock. In this report, a series of cspA-lacZ fusions having a 26- to 32-base deletion in the 5′-UTR were constructed to examine the roles of specific regions within the 5′-UTR in cspA expression. It was found that none of the deletion mutations had significant effects on the stability of mRNA at both 37 and 15°C. However, two mutations (Δ56-86 and Δ86-117) caused a substantial increase of β-galactosidase activity at 37°C, indicating that the deleted regions contain a negative cis element(s) for translation. A mutation (Δ2-27) deleting the highly conserved cold box sequence had little effect on cold shock induction of β-galactosidase. Interestingly, three mutations (Δ28-55, Δ86-117, and Δ118-143) caused poor cold shock induction of β-galactosidase. In particular, the Δ118-143 mutation reduced the translation efficiency of the cspA mRNA to less than 10% of that of the wild-type construct. The deleted region contains a 13-base sequence named upstream box (bases 123 to 135), which is highly conserved in cspA, cspB, cspG, and cspI, and is located 11 bases upstream of the Shine-Dalgarno (SD) sequence. The upstream box might be another cis element involved in translation efficiency of the cspA mRNA in addition to the SD sequence and the downstream box sequence. The relationship between the mRNA secondary structure and translation efficiency is discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=103761Documentos Relacionados
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