Role of Escherichia coli cspA promoter sequences and adaptation of translational apparatus in the cold shock response

Abstract

A shift in growth temperature from 37 degrees C to 15 degrees C leads to a dramatic increase in the level of CspA, the major cold shock protein of Escherichia coli. To investigate the molecular basis of this induction, we considered the relevance of transcriptional and posttranscriptional controls by analyzing the steady-state levels of transcripts and the expression of reporter genes in cells carrying a set of cspA promoter fragments of variable length fused to lacZ or cat genes. We demonstrate that: (i) the core cspA promoter (from -40 to +16) responds to cold shock and a mutation at -36 increases the relative activity of the promoter at low temperature by threefold; (ii) the sequences upstream of -40 have a positive effect on expression at 37 degrees C, but no effect on the cold shock response; (iii) by virtue of their influence on mRNA stability, the downstream sequences (from +81 to +165) reduce expression at 37 degrees C and increase the intensity of the cold shock response; (iv) mutations in the GCACATCA and CCAAT motifs, present at +1/-4 and between the -10 and -35 elements, respectively, do not affect the cold shock response of the cspA promoter; (v) following cold shock, a modification of the protein synthetic machinery takes place that allows preferential translation of cspA mRNA relative to the non-cold shock cat and lacZ mRNAs. The quantitatively modest transcriptional activation shown by the core promoter of cspA following cold shock suggests that transcriptional activation can significantly contribute to cold shock induction only when coupled to posttranscriptional controls, such as alterations in mRNA stability and the translational apparatus.

Cold-stress-induced de novo expression of infC and role of IF3 in cold-shock translational bias

“…Previous studies have shown that one of the main mechanisms by which cold-stressed cells attain an increased expression of the cold-shock genes is by modification of the translational apparatus, which leads to the selective stimulation of cold-shock mRNA translation and to the repression of ''non-cold-shock'' mRNA translation at low temperature (Brandi et al 1996;Goldenberg et al 1997;Giuliodori et al 2004). This ''cold-shock translational bias'' strongly depends upon initiation factor IF3, whose cellular level is increased more than threefold during the first few hours of cold adaptation at 10°C (Gualerzi et al 2003;Giuliodori et al 2004).…”

“…Cold-shock translational bias, namely, the condition that favors translation at low temperature of cold-shock mRNAs, is one of the main and most characteristic mechanisms by which the cell ensures the selective expression of its cold-shock genes (Brandi et al 1996;Goldenberg et al 1997;Giuliodori et al 2004). Translational bias occurs during the 3-5 h (depending upon the temperature) acclimation phase, which begins after the cold stress and ends when the cells resume slow growth at low temperature.…”

Coping with the cold: the cold shock response in the Gram-positive soil bacterium Bacillus subtilis

“…Interestingly, the E. coli cspA gene reported to be cold inducible at the transcriptional level, as well as cold-inducible cspB and cspC genes in B. subtilis, contain an AT-rich UP-element Goldenberg et al 1997;Graumann et al 1997;Mitta et al 1997;Kaan et al 1999) that, apart from being directly recognized by the ␣-subunit of RNA polymerase as demonstrated for E. coli (Ross et al 1993), might serve as a strand-opening hot-spot during cold shock. In fact, in B. subtilis, the negative supercoil of the DNA increases after cold shock (Grau et al 1994;Krispin & Allmansberger 1995).…”

RNA remodeling and gene regulation by cold shock proteins

“…The cspA transcript undergoes a 4-5-fold increase upon cold shock as revealed by studies using reporter gene fusions the reporter genes, 58,59 primer extension, northern blot analysis and DNA microarray analysis of the global transcript profile of cold-shocked cells. 39 No additional factors (other than cold) are necessary for cspA induction.…”

“…Certain elements seem to enhance the level of cspA promoter activity. These include (1) an AT-rich sequence (UP element) immediately upstream of the -35 region; 58,59 and (2) an extended -10 box a TGn motif preceding the -10 box. However, none of these elements seem to specifically contribute to low-temperature activity of the cspA promoter.…”