title: The CarD/CarG regulatory complex is required for the action of several members of the large set of Myxococcus xanthus extracytoplasmic function σ factors.
abstract: Extracytoplasmic function (ECF) σ factors are critical players in signal transduction networks involved in bacterial response to environmental changes. The Myxococcus xanthus genome reveals ∼45 putative ECF-σ factors, but for the overwhelming majority, the specific signals or mechanisms for selective activation and regulation remain unknown. One well-studied ECF-σ, CarQ, binds to its anti-σ, 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-σ, activates its own expression in a CarD/CarG-dependent manner but is inhibited when specifically bound to the N-terminal zinc-binding anti-σ domain of its cognate anti-σ, DdvA. Interestingly, we find that the autoregulatory action of 11 other ECF-σ 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-σ 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.
authors.affiliation: Departamento de Genética y Microbiología, Área de Genética (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, Murcia, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Abellón-Ruiz
authors.forename: Diego
authors.initials: D
authors.lastname: Bernal-Bernal
authors.forename: María
authors.initials: M
authors.lastname: Abellán
authors.forename: Marta
authors.initials: M
authors.lastname: Fontes
authors.forename: S
authors.initials: S
authors.lastname: Padmanabhan
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Murillo
authors.forename: Montserrat
authors.initials: M
authors.lastname: Elías-Arnanz
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D008027:Light; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; C100589:CarD protein, Myxococcus xanthus; D012808:Sigma Factor; D015534:Trans-Activators