RNA thermometer

This structural transition can then expose or occlude important regions of RNA such as a ribosome binding site, which then affects the translation rate of a nearby protein-coding gene.

[11] This protein is involved in selection of either a lytic or lysogenic life cycle in λ phage, with high concentrations of cIII promoting lysogeny.

[10][12] This RNA thermometer is now thought to encourage entry to a lytic cycle under heat stress in order for the bacteriophage to rapidly replicate and escape the host cell.

[2] C. reinhardtii’s RNA thermometer research is the entryway to observing the chloroplast of photosynthetic organisms for gene regulation and how it can be used for agriculture at some point in the future since it helps plants get accustomed to external temperature.

[9] Generally these RNA elements range in length from 60 to 110 nucleotides[21] and they typically contain a hairpin with a small number of mismatched base pairs which reduce the stability of the structure, thereby allowing easier unfolding in response to a temperature increase.

Since these noncanonical base pairs are relatively unstable, increased temperature causes local melting of the RNA structure in this region, exposing the Shine-Dalgarno sequence.

[24] However, the secondary structure of such short RNA thermometers can be sensitive to mutation, as a single base change can render the hairpin inactive in vivo.

[17] As temperature increases, the hairpin structure can 'melt' and expose the RBS or Shine-Dalgarno sequence to permit binding of the small ribosomal subunit (30S), which then assembles other translation machinery.

[1] The start codon, typically found 8 nucleotides downstream of the Shine-Dalgarno sequence,[17] signals the beginning of a protein-coding gene which is then translated to a peptide product by the ribosome.

In addition to this cis-acting mechanism, a lone example of a trans-acting RNA thermometer has been found in RpoS mRNA where it is thought to be involved in the starvation response.

[22] For example, the expression of two 7kDa proteins are regulated by an RNA thermometer in the thermophilic bacterium Thermus thermophilus[28] and a similar mechanism has been identified in Enterobacteriales.