Disease relevance of rsbU

• A natural rsbU mutant of Staphylococcus aureus, unable to activate the alternative transcription factor sigma(B) via the RsbU pathway and therefore forming unpigmented colonies, produced first-step teicoplanin-resistant mutants upon selection for growth in the presence of teicoplanin, of which the majority were of an intense orange color [1].
• Transposon mutagenesis of rsbU leads to a biofilm-negative phenotype in Staphylococcus epidermidis [2].
• The rsbU defect of strain 8325-4 has recently been repaired, and we used this strain (SH1000), along with its isogenic sigB-negative mutant, to investigate the contributions of RsbU and SigB in a murine model of septic arthritis [3].

High impact information on rsbU

• Salicylic acid activates sigma factor B by rsbU-dependent and -independent mechanisms [4].
• Insertion of Tn917 into rsbU, a positive regulator of alternative sigma factor sigma(B), led to a biofilm-negative phenotype and almost undetectable PIA production [5].
• The insertion site was the same in both of the mutants and was located in the first gene, rsbU, of an operon highly homologous to the sigB operons of Staphylococcus aureus and Bacillus subtilis [5].
• Transcriptional analysis and a sarP1-sarP2-sarP3 (sarP1-P2-P3)-driven firefly luciferase (luc+) reporter gene fusion demonstrated a strong sigma(B) activity- and growth phase-dependent increase in sar expression that was totally absent in either rsbU or Delta rsbUVWsigB mutants [6].

Biological context of rsbU

• Interestingly, most sigB deletion phenotypes were only seen in S. aureus COL and Newman and not in 8325, which was found to contain an 11-bp deletion in the regulator gene rsbU [7].

Other interactions of rsbU

• However, RN6390 was recently shown to have a mutation in rsbU that results in a phenotype resembling that of a sigB mutant (I. Kullik et al., J. Bacteriol. 180:4814-4820, 1998) [8].

Analytical, diagnostic and therapeutic context of rsbU

• We established an arbitrary PCR for the rapid and easy identification of Tn917 insertion sites in Staphylococcus epidermidis with six independent, well-characterized biofilm-negative Tn917 transposon mutants, which were clustered in the icaADBC gene locus or harbor Tn917 in the regulatory gene rsbU [9].

References