Rsd family proteins make simultaneous interactions with regions 2 and 4 of the primary sigma factor

• Published in: Molecular microbiology Vol. 70; no. 5; pp. 1136 - 1151
• Main Authors: Yuan, Andy H, Gregory, Brian D, Sharp, Josh S, McCleary, Katherine D, Dove, Simon L, Hochschild, Ann
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.12.2008; Blackwell Publishing Ltd; Blackwell
• Subjects: Amino Acid Substitution; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological and medical sciences; DNA, Bacterial - genetics; DNA-Directed RNA Polymerases - metabolism; E coli; Escherichia coli; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene expression; Gene Expression Regulation, Bacterial; Genes, Bacterial; Microbiology; Mutation; Plasmids; Protein Binding; Proteins; Pseudomonas aeruginosa; Pseudomonas aeruginosa - genetics; Pseudomonas aeruginosa - metabolism; Pyocyanine - biosynthesis; Repressor Proteins - genetics; Repressor Proteins - metabolism; RNA polymerase; Sigma Factor - metabolism; Trans-Activators - genetics; Trans-Activators - metabolism; Transcription, Genetic; Microbiology; Initiation factor σ; Protein
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2008.06462.x

Bacterial anti-σ factors typically regulate σ factor function by restricting the access of their cognate σ factors to the RNA polymerase (RNAP) core enzyme. The Escherichia coli Rsd protein forms a complex with the primary σ factor, σ⁷⁰, inhibits σ⁷⁰-dependent transcription in vitro, and has been proposed to function as a σ⁷⁰-specific anti-σ factor, thereby facilitating the utilization of alternative σ factors. In prior work, Rsd has been shown to interact with conserved region 4 of σ⁷⁰, but it is not known whether this interaction suffices to account for the regulatory functions of Rsd. Here we show that Rsd and the Rsd orthologue AlgQ, a global regulator of gene expression in Pseudomonas aeruginosa, interact with conserved region 2 of σ⁷⁰. We show further that Rsd and AlgQ can interact simultaneously with regions 2 and 4 of σ⁷⁰. Our findings establish that the abilities of Rsd and AlgQ to interact with σ⁷⁰ region 2 are important determinants of their in vitro and in vivo activities.