Extended -10 motif is critical for activity of the cspA promoter but does not contribute to low-temperature transcription

Bacterial promoters belonging to the extended -10 class contain a conserved TGn motif upstream of the -10 promoter consensus element. Open promoter complexes can be formed on some extended -10 Escherichia coli promoters at temperatures as low as 6°C, when complexes on most promoters are closed. The promoter of cspA, a gene that codes for the major cold shock protein CspA of E. coli, contains an extended -10 motif. CspA is dramatically induced upon temperature downshift from 37 to 15°C, and its cold shock induction has been attributed to transcription, translation, and mRNA stabilization effects. Here, we show that though the extended -10 motif is critical for high-level expression of cspA, it does not contribute to low-temperature expression. In fact, transcription from the wild-type cspA promoter is cold sensitive in vitro and in vivo. Thus, transcription appears to play little or no role in low-temperature induction of cspA expression.