PHEROMONE-INDUCIBLE EXPRESSION OF AN AGGREGATION PROTEIN IN ENTEROCOCCUS-FAECALIS REQUIRES INTERACTION OF A PLASMID-ENCODED RNA WITH COMPONENTS OF THE RIBOSOME

Transfer of the conjugative plasmid pCF10 from Enterococcus faecalis d onor strains is induced by a peptide pheromone (cCF10) secreted by rec ipient cells. High-efficiency transfer requires expression of an aggre gation protein (Asc10) encoded by the prgB gene and positively regulat ed by genes in a region 3-5 kb upstream, containing prgQ-R-S. Transcri ptional fusion data reported here support the results of recent molecu lar analysis of the 5' ends of prgB transcripts which indicated that p rgB transcription occurs by readthrough from the prgQ promoter. A 530- nucleotide prgQ-encoded RNA molecule (QL) with rRNA-like domains is re quired for Asc10 production. QL and cCF10 were found to interact with the L6 and S5 ribosomal proteins, respectively. Mutational analysis of QL indicates that this RNA may also directly interact with 16S RNA. Q L is present in ribosomes translating the prgB message, and pheromone cCF10 may affect the association of this RNA with translation complexe s. Results suggest that the positive regulatory molecules act post-tra nscriptionally on the polycistronic message and modify a ribosome popu lation to enhance pheromone-induced translation of prgB.