The CarD/CarG regulatory complex is required for the action of several members of the large set of Myxococcus xanthus extracytoplasmic function sigma factors

作者：Abellon Ruiz Javier; Bernal Bernal Diego; Abellan Maria; Fontes Marta; Padmanabhan S; Murillo Francisco J^*; Elias Arnanz Montserrat

来源：Environmental Microbiology, 2014, 16(8): 2475-2490.

DOI：10.1111/1462-2920.12386

Extracytoplasmic ECF) sigma factors are critical players in signal transduction networks involved in bacterial response to environmental changes. The Myxococcus xanthus genome reveals similar to 45 putative ECF-sigma factors, but for the overwhelming majority, the specific signals or mechanisms for selective activation and regulation remain unknown. One well-studied ECF-sigma, CarQ, binds to its anti-sigma, CarR, and is inactive in the dark but drives its own expression from promoter P-QRS on illumination. This requires the CarD/CarG complex, the integration host factor (IHF) and a specific CarD-binding site upstream of P-QRS. Here, we show that DdvS, a previously uncharacterized ECF-sigma, activates its own expression in a CarD/CarG-dependent manner but is inhibited when specifically bound to the N-terminal zinc-binding anti-sigma domain of its cognate anti-sigma, DdvA. Interestingly, we find that the autoregulatory action of 11 other ECF-sigma factors studied here depends totally or partially on CarD/CarG but not IHF. In silico analysis revealed possible CarD-binding sites that may be involved in direct regulation by CarD/CarG of target promoter activity. CarD/CarG-linked ECF-sigma regulation likely recurs in other myxobacteria with CarD/CarG orthologous pairs and could underlie, at least in part, the global regulatory effect of the complex on M. xanthus gene expression.

• 出版日期2014-8