The bacteriophage T4 AsiA protein contacts the beta-flap domain of RNA polymerase.
To initiate transcription from specific promoters, the bacterial RNA polymerase (RNAP) core enzyme must associate with the initiation factor sigma, which contains determinants that allow sequence-specific interactions with promoter DNA. Most bacteria contain several sigma factors, each of which directs recognition of a distinct set of promoters. A large and diverse family of proteins known as "anti-sigma factors" regulates promoter utilization by targeting specific sigma factors. The founding member of this family is the AsiA protein of bacteriophage T4. AsiA specifically targets the primary sigma factor in Escherichia coli, sigma(70), and inhibits transcription from the major class of sigma(70)-dependent promoters. AsiA-dependent transcription inhibition has been attributed to a well-documented interaction between AsiA and conserved region 4 of sigma(70). Here, we establish that efficient AsiA-dependent transcription inhibition also requires direct protein-protein contact between AsiA and the RNAP core. In particular, we demonstrate that AsiA contacts the flap domain of the RNAP beta-subunit (the beta-flap). Our findings support the emerging view that the beta-flap is a target site for regulatory proteins that affect RNAP function during all stages of the transcription cycle.
Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Andy H
AH
Yuan
Bryce E
BE
Nickels
Ann
A
Hochschild
D019943:Amino Acid Substitution; D017122:Bacteriophage T4 / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012808:Sigma Factor / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
C078876:AsiA protein, Enterobacteria phage T4; D012808:Sigma Factor; D014764:Viral Proteins; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases