The cspA mRNA is a thermosensor that modulates translation of the cold-shock protein CspA.
Cold induction of cspA, the paradigm Escherichia coli cold-shock gene, is mainly subject to posttranscriptional control, partly promoted by cis-acting elements of its transcript, whose secondary structure at 37 degrees C and at cold-shock temperature has been elucidated here by enzymatic and chemical probing. The structures, which were also validated by mutagenesis, demonstrate that cspA mRNA undergoes a temperature-dependent structural rearrangement, likely resulting from stabilization in the cold of an otherwise thermodynamically unstable folding intermediate. At low temperature, the "cold-shock" structure is more efficiently translated and somewhat less susceptible to degradation than the 37 degrees C structure. Overall, our data shed light on a molecular mechanism at the basis of the cold-shock response, indicating that cspA mRNA is able to sense temperature downshifts, adopting functionally distinct structures at different temperatures, even without the aid of trans-acting factors. Unlike with other previously studied RNA thermometers, these structural rearrangements do not result from melting of hairpin structures.
Laboratory of Genetics, Department of Biology MCA, University of Camerino, 62032 Camerino (MC), Italy.
Anna Maria
AM
Giuliodori
Fabio
F
Di Pietro
Stefano
S
Marzi
Benoit
B
Masquida
Rolf
R
Wagner
Pascale
P
Romby
Claudio O
CO
Gualerzi
Cynthia L
CL
Pon
D020121:5' Untranslated Regions; D000064:Acclimatization; D057773:Cold Shock Proteins and Peptides; D003080:Cold Temperature; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry / Q000502:physiology*
D020121:5' Untranslated Regions; D057773:Cold Shock Proteins and Peptides; C498192:CspA protein, E coli; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger