On the role of mRNA secondary structure in bacterial translation.

Messenger RNA (mRNA) is no longer considered as a mere informational molecule whose sole function is to convey the genetic information specified by DNA to the ribosome. Beyond this primary function, mRNA also contains additional instructions that influence the way and the extent to which this message is translated by the ribosome into protein(s). Indeed, owing to its intrinsic propensity to quickly and dynamically fold and form higher order structures, mRNA exhibits a second layer of structural information specified by the sequence itself.

Stem-Loop Structures within mRNA Coding Sequences Activate Translation Initiation and Mediate Control by Small Regulatory RNAs.

Initiation is the rate-limiting step of translation, and in bacteria, mRNA secondary structure has been extensively reported as limiting the efficiency of translation by occluding the ribosome-binding site. In striking contrast with this inhibitory effect, we report here that stem-loop structures located within coding sequences instead activate translation initiation of the Escherichia coli fepA and bamA mRNAs involved in iron acquisition and outer membrane proteins assembly, respectively. Both structures promote ribosome binding in vitro, independently of their nucleotide sequence.

Mechanistic study of base-pairing small regulatory RNAs in bacteria.

In all three kingdoms of life, RNA is not only involved in the expression of genetic information, but also carries out extremely diverse cellular functions. This versatility is essentially due to the fact that RNA molecules can exploit the power of base pairing to allow them to fold into a wide variety of structures through which they can perform diverse roles, but also to selectively target and bind to other nucleic acids. This is true in particular for bacterial small regulatory RNAs that act by imperfect base-pairing with target mRNAs, and thereby control their expression through different mechanisms.

The sRNA RyhB regulates the synthesis of the Escherichia coli methionine sulfoxide reductase MsrB but not MsrA.

Controlling iron homeostasis is crucial for all aerobically grown living cells that are exposed to oxidative damage by reactive oxygen species (ROS), as free iron increases the production of ROS. Methionine sulfoxide reductases (Msr) are key enzymes in repairing ROS-mediated damage to proteins, as they reduce oxidized methionine (MetSO) residues to methionine. E.

Post-transcriptional control of the Escherichia coli PhoQ-PhoP two-component system by multiple sRNAs involves a novel pairing region of GcvB.

PhoQ/PhoP is a central two-component system involved in magnesium homeostasis, pathogenicity, cell envelope composition, and acid resistance in several bacterial species. The small RNA GcvB is identified here as a novel direct regulator of the synthesis of PhoQ/PhoP in Escherichia coli, and this control relies on a novel pairing region of GcvB. After MicA, this is the second Hfq-dependent small RNA that represses expression of the phoPQ operon.