Turned On by the Cold

Science Signaling  26 Jan 2010:
Vol. 3, Issue 106, pp. ec26-e26
DOI: 10.1126/scisignal.3106ec26

Changes in temperature can cause cellular damage by altering the structure of biological molecules. Therefore, prokaryotes and eukaryotes have developed mechanisms to sense and adapt to changes in temperature in order to survive under changing environmental conditions. In Escherichia coli, cold triggers the induction of a set of cold-shock genes, among which the one encoding CspA is one of the earliest induced through primarily posttranscriptional mechanisms. Giuliodori et al. used enzymatic and chemical accessibility assays, along with temperature gradient gel electrophoresis, to show that cspA mRNA exhibited different structures at 10° or 20°C compared to that at 37°C. They found that the structural differences required the coding region and were not exhibited by truncated versions of the mRNA containing only the 5′-untranslated region. At 37°C, the mRNA adopted a conformation that limited access to the translational start codon and the ribosome binding site (represented by the Shine-Dalgarno sequence), whereas at either 10° or 20°C, these regions were more susceptible to enzymatic cleavage or chemical adduction. Mutational analysis was consistent with the structural models. Furthermore, in vitro ribosome binding assays and translation assays showed that the cold-stabilized mRNA bound ribosomes and start tRNAs more efficiently, as well as translated protein more quickly, than did mRNAs folded at 37°C. Thus, cspA mRNA serves as a cold sensor, allowing its encoded protein CspA to act as a first responder in the adaptive response to cold (see Breaker for commentary).

A. M. Giuliodori, F. Di Pietro, S. Marzi, B. Masquida, R. Wagner, P. Romby, C. O. Gualerzi, C. L. Pon, The cspA mRNA is a thermosensor that modulates translation of the cold-shock protein CspA. Mol. Cell. 37, 21–33 (2010). [Online Journal]

R. R. Breaker, RNA switches out in the cold. Mol. Cell 37, 1–2 (2010). [Online Journal]