Bacteriophage T4 MotA activator and the ß-flap tip of RNA polymerase target the same set of σ70 carboxyl-terminal residues.
J Biol Chem
; 286(45): 39290-6, 2011 Nov 11.
Article
in En
| MEDLINE
| ID: mdl-21911499
ABSTRACT
Sigma factors, the specificity subunits of RNA polymerase, are involved in interactions with promoter DNA, the core subunits of RNA polymerase, and transcription factors. The bacteriophage T4-encoded activator, MotA, is one such factor, which engages the C terminus of the Escherichia coli housekeeping sigma factor, σ(70). MotA functions in concert with a phage-encoded co-activator, AsiA, as a molecular switch. This process, termed sigma appropriation, inhibits host transcription while activating transcription from a class of phage promoters. Previous work has demonstrated that MotA contacts the C terminus of σ(70), H5, a region that is normally bound within RNA polymerase by its interaction with the ß-flap tip. To identify the specific σ(70) residues responsible for interacting with MotA and the ß-flap tip, we generated single substitutions throughout the C terminus of σ(70). We find that MotA targets H5 residues that are normally engaged by the ß-flap. In two-hybrid assays, the interaction of σ(70) with either the ß-flap tip or MotA is impaired by alanine substitutions at residues Leu-607, Arg-608, Phe-610, Leu-611, and Asp-613. Transcription assays identify Phe-610 and Leu-611 as the key residues for MotA/AsiA-dependent transcription. Phe-610 is a crucial residue in the H5/ß-flap tip interaction using promoter clearance assays with RNA polymerase alone. Our results show how the actions of small transcriptional factors on a defined local region of RNA polymerase can fundamentally change the specificity of polymerase.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Sigma Factor
/
Transcription Factors
/
Viral Proteins
/
DNA-Directed RNA Polymerases
/
Bacteriophage T4
/
Escherichia coli Proteins
/
DNA-Binding Proteins
/
Escherichia coli
Type of study:
Prognostic_studies
Language:
En
Journal:
J Biol Chem
Year:
2011
Type:
Article
Affiliation country:
United States