PHEROMONE CCF10 AND PLASMID PCF10-ENCODED REGULATORY MOLECULES ACT POSTTRANSCRIPTIONALLY TO ACTIVATE EXPRESSION OF DOWNSTREAM CONJUGATION FUNCTIONS

Expression of aggregation protein Asc10 from the prgB gene of conjugat ive plasmid pCF10 in Enterococcus faecalis is induced by the peptide p heromone cCF10. Genes required for Asc10 production, prgQ and prgS, li e 3-5 kb upstream, but can function at much greater distances. The prg Q transcripts encode a pheromone inhibitor peptide (iCF10) at the extr eme 5' end. Neither production of this peptide nor translation of the 5' end of prgQ transcripts was found to be necessary for prgB expressi on. Pheromone cCF10 is required to activate prgB expression, even in t he absence of iCF10 production, and does not affect initiation of tran scription. The prgS gene encodes a 10.5 kDa protein that appears to be required for translation of prgS, and a non-coding RNA at the 3' end of prgS may be required for readthrough of transcription to prgS from the prgQ promoter. Although the entire positive control region is tran scribed constitutively from the prgQ promoter, translation of PrgS and transcriptional readthrough to prgB occur only after induction with p heromone. The combined data are consistent with a model in which the p ositive regulatory molecules and pheromone cCF10 activate prgB express ion post-transcriptionally.