Activation of alpha-toxin translation in Staphylococcus aureus by the trans-encoded antisense RNA, RNAIII.
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.
Morfeldt
E
E
Microbiology and Tumorbiology Center, Karolinska Institute, Stockholm, Sweden.
Taylor
D
D
von Gabain
A
A
Arvidson
S
S
D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D016372:RNA, Antisense / Q000235:genetics* / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013211:Staphylococcus aureus / Q000235:genetics* / Q000254:growth & development
D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D016372:RNA, Antisense; D012329:RNA, Bacterial; D012333:RNA, Messenger; C096035:RNAIII, Staphylococcus aureus; C021091:staphylococcal alpha-toxin