Activation of alpha-toxin translation in Staphylococcus aureus by the trans-encoded antisense RNA, RNAIII

EMBO J. 1995 Sep 15;14(18):4569-77.


The synthesis of virulence factors in Staphylococcus aureus is controlled by a regulatory RNA molecule, RNAIII, encoded by the agr locus. Transcription of genes coding for secreted toxins and enzymes is stimulated, while transcription of cell-surface protein genes is repressed by RNAIII. In the case of staphylococcal alpha-toxin, RNAIII also seems to stimulate translation by an independent mechanism. In this report we show that in a mutant lacking RNAIII the rate of alpha-toxin (hla) production relative to the cellular concentration of hla mRNA was reduced 10-fold as compared with the wild-type strain. A 75% complementarity between the 5' end of RNAIII and the 5' untranslated region of the hla transcript suggests a direct interaction between the RNAs. A complex of RNAIII and hla mRNA was demonstrated in extracts of total RNA from the wild-type strain, and also with in vitro synthesized RNAs. Ribonuclease T1 digestion experiments revealed that the ribosome binding site of the hla transcript is blocked by intramolecular base-pairing. Hybridization with RNAIII prevents this intramolecular base-pairing and makes the hla mRNA accessible for translation initiation. This is, to our knowledge, the first example of an 'antisense RNA' that stimulates translation of the target mRNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Toxins / biosynthesis
  • Bacterial Toxins / genetics*
  • Base Sequence
  • Blotting, Northern
  • Electrophoresis, Agar Gel
  • Electrophoresis, Polyacrylamide Gel
  • Gene Expression Regulation, Bacterial*
  • Hemolysin Proteins / biosynthesis
  • Hemolysin Proteins / genetics*
  • Molecular Sequence Data
  • Mutation
  • Nucleic Acid Conformation
  • Protein Biosynthesis*
  • RNA, Antisense / genetics*
  • RNA, Antisense / metabolism
  • RNA, Bacterial / genetics*
  • RNA, Bacterial / metabolism
  • RNA, Messenger / metabolism
  • Sequence Analysis, DNA
  • Staphylococcus aureus / genetics*
  • Staphylococcus aureus / growth & development


  • Bacterial Toxins
  • Hemolysin Proteins
  • RNA, Antisense
  • RNA, Bacterial
  • RNA, Messenger
  • RNAIII, Staphylococcus aureus
  • staphylococcal alpha-toxin

Associated data

  • GENBANK/X01645