CspA mRNA 5′ UTR explained

cspA 5' UTR
Symbol:	cspA 5'UTR
Rfam:	RF01766
Rna Type:	Cis-reg Thermoregulator;
Tax Domain:	Enterobacteriales

cspA mRNA 5' UTR is the untranslated region of the cspA gene, which is important in the cold shock response in Enterobacteriales such as E. coli. The 5' UTR element acts as an RNA thermometer, regulating the expression of cspA in response to temperature.^[1] By regulating temperature, cspA proteins carry out the vital function of homeostasis.

The 5' UTR was first suspected to be significant when mutations within this region of cspA significantly increased the stability of the transcript at 37°C.^[2]

The secondary structure of cspA mRNA changes in response to temperature; at 37 °C the transcript is unstable and less efficiently translated than at lower temperatures.^[3] Unlike other RNA thermometers (such as FourU), the secondary structure is not reliant on the melting of a hairpin in order to affect gene expression. Instead, in temperatures below 20 °C a cis-regulatory region of ncRNA in the 5' UTR of cspA presents the Shine-Dalgarno sequence and AUG start codon to the ribosome in a more accessible way. The precise mechanism for changing the mRNA conformation is unknown. cspA protein is then produced in significantly higher quantities, making up over 2% of the cell's proteome during cold shock.^[4] cspA protein binds Hfq, which upregulates production of sigma factors which mediate a stress response.^[5]

See also

• Hfq binding sRNA
• ROSE element

Further reading

• Goldstein J, Pollitt NS, Inouye M . Major cold shock protein of Escherichia coli . Proc. Natl. Acad. Sci. U.S.A. . 87 . 1 . 283–287 . January 1990 . 2404279 . 53247 . 10.1073/pnas.87.1.283. 1990PNAS...87..283G . free .
• Gualerzi CO, Giuliodori AM, Pon CL . Transcriptional and post-transcriptional control of cold-shock genes . J. Mol. Biol. . 331 . 3 . 527–539 . August 2003 . 12899826 . 10.1016/S0022-2836(03)00732-0.
• Narberhaus F, Waldminghaus T, Chowdhury S . RNA thermometers . FEMS Microbiol. Rev. . 30 . 1 . 3–16 . January 2006 . 16438677 . 10.1111/j.1574-6976.2005.004.x . free .
• De La Fuente . M. . Valera . S. . Martínez-Guitarte . J. L. . 10.1016/j.febslet.2012.10.018 . NcRNAs and thermoregulation: A view in prokaryotes and eukaryotes . FEBS Letters . 586 . 23 . 4061–4069 . 2012 . 23098758 . free .

Notes and References

1. Giuliodori AM, Di Pietro F, Marzi S . The cspA mRNA is a thermosensor that modulates translation of the cold-shock protein CspA . Mol. Cell . 37 . 1 . 21–33 . January 2010 . 20129052 . 10.1016/j.molcel.2009.11.033 . etal. free .
2. Yamanaka K, Mitta M, Inouye M . Mutation analysis of the 5' untranslated region of the cold shock cspA mRNA of Escherichia coli . J. Bacteriol. . 181 . 20 . 6284–6291 . October 1999 . 10.1128/JB.181.20.6284-6291.1999 . 10515916 . 103761 .
3. Breaker RR . RNA switches out in the cold . Mol. Cell . 37 . 1 . 1–2 . January 2010 . 20129048 . 10.1016/j.molcel.2009.12.032. 5315359 .
4. Brandi A, Spurio R, Gualerzi CO, Pon CL . Massive presence of the Escherichia coli 'major cold-shock protein' CspA under non-stress conditions . EMBO J. . 18 . 6 . 1653–1659 . March 1999 . 10075935 . 1171252 . 10.1093/emboj/18.6.1653 .
5. Hankins JS, Denroche H, Mackie GA . Interactions of the RNA-binding protein Hfq with cspA mRNA, encoding the major cold shock protein . J. Bacteriol. . 192 . 10 . 2482–2490 . May 2010 . 20233932 . 10.1128/JB.01619-09 . 2863566.