Function
Global regulator with both positive and negative effects that controls expression of several virulence factors and biofilm formation process in a cell density-dependent manner. In a strain-dependent manner plays a role in multidrug resistance mechanism. Is required for transcription of primary transcripts RNAII and RNAIII generated by agr (virulence accessory gene regulator) locus. Acts as a transcriptional activator of the genes encoding, among others, for fibronectin binding proteins (fnbA and fnbB), hemolysins (hla, hld, hlgB and hlgC), serine proteases (splA, splB, splD and splF) and of the bap gene, which is essential for biofilm development in some strains. Negatively regulates the expression of the genes for protein A (spa), lipase (lip), thermonuclease (nuc), immunodominant staphylococcal antigen B (isaB), staphylococcal serine and cysteine proteases (sspA and sspB), staphostatin B (sspC), metalloprotease aureolysin (aur) and collagen adhesin (cna). Probably activates the development of biofilm by both enhancing the ica operon transcription and suppressing the transcription of either a protein involved in the turnover of PIA/PNAG or a repressor of its synthesis, whose expression would be sigma-B-dependent.