Pheromone-inducible expression of an aggregation protein in Enterococcus faecalis requires interaction of a plasmid-encoded RNA with components of the ribosome.

Abstract

Transfer of the conjugative plasmid pCF10 from Enterococcus faecalis donor strains is induced by a peptide pheromone (cCF10) secreted by recipient cells. High-efficiency transfer requires expression of an aggregation protein (Asc10) encoded by the prgB gene and positively regulated by genes in a region 3-5 kb upstream, containing prgQ-R-S. Transcriptional fusion data reported here support the results of recent molecular analysis of the 5' ends of prgB transcripts which indicated that prgB transcription occurs by readthrough from the prgQ promoter. A 530-nucleotide prgQ-encoded RNA molecule (Q(L)) with rRNA-like domains is required for Asc10 production. Q(L) and cCF10 were found to interact with the L6 and S5 ribosomal proteins, respectively. Mutational analysis of Q(L) 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 complexes. Results suggest that the positive regulatory molecules act post-transcriptionally on the polycistronic message and modify a ribosome population to enhance pheromone-induced translation of prgB.