Interactions of the non-coding RNA DsrA and RpoS mRNA with the 30 S ribosomal subunit.
Expression of sigma(s), the gene product of rpoS, is controlled translationally in response to many environmental stresses. DsrA, a small 87-nucleotide non-coding RNA molecule, acts to increase translational efficiency of RpoS mRNA under some growth conditions. In this work, we demonstrate that DsrA binds directly to the 30 S ribosomal subunit with an observed equilibrium affinity of 2.8 x 10(7) m(-1). DsrA does not compete with RpoS mRNA or tRNA(f)(Met) for binding to the 30 S subunit. The 5' end of DsrA binds to 30 S subunits with an observed equilibrium association constant of 2.0 x 10(6) m(-1), indicating that the full affinity of the interaction requires the entire DsrA sequence. In order to investigate translational efficiency of RpoS mRNA, we examined both ribosome-binding site accessibility and the binding of RpoS mRNA to 30 S ribosomal subunits. We find that that ribosome-binding site accessibility is modulated as a function of divalent cation concentration during mRNA renaturation and by the presence of an antisense sequence that binds to nucleotides 1-16 of the RpoS mRNA fragment. The ribosome-binding site accessibility correlates with the amount of RpoS mRNA participating in 30 S-mRNA "pre-initiation" translational complex formation and provides evidence that regulation follows a competitive model of regulation.
Worhunsky
David J
DJ
Department of Chemistry and Program in Biological Chemistry, Bates College, Lewiston, Maine 04240, USA.
Godek
Kristina
K
Litsch
Sarah
S
Schlax
Paula Jean
PJ
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D008274:Magnesium / Q000494:pharmacology; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry*; D022661:RNA, Untranslated / Q000737:chemistry*; D012270:Ribosomes / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D012333:RNA, Messenger; D022661:RNA, Untranslated; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D008274:Magnesium