title: Activator-sigma interaction: A hydrophobic segment mediates the interaction of a sigma family promoter recognition protein with a sliding clamp transcription activator.
abstract: Activation of transcription at bacteriophage T4 late promoters and coupling of late transcription to concurrent replication requires a peculiar transcriptional activator, the gp45 sliding clamp of the T4 DNA polymerase. In order to activate transcription, the topologically DNA-linked trimeric gp45 must interact with two T4-encoded RNA polymerase-binding proteins, the gp33 co-activator, and the gp55 late sigma factor. The carboxy termini of gp55 and gp33 share a similar sequence, which has been shown to be required for response of late transcription to activation by gp45. Alanine-scanning mutagenesis of the C terminus of gp55 shows that residues within the short hydrophobic sequence L(D/A)FLYE, are necessary for gp55 to bind to gp45, and to respond maximally to transcriptional activation by gp45. When fused to GST, the peptide SLDFLYE suffices for specific gp45 binding. Thus, it constitutes the main gp55 epitope for gp45 interaction.
authors.affiliation: Department of Biology and Center for Molecular Genetics, University of California, 9500 Gilman Drive, San Diego, CA, 92093-0634, USA. kwong@biomail.ucsd.edu
authors.forename: K
authors.initials: K
authors.lastname: Wong
authors.forename: E P
authors.initials: EP
authors.lastname: Geiduschek
mesh_terms: D000409:Alanine / Q000235:genetics; D017122:Bacteriophage T4 / Q000235:genetics*; D001665:Binding Sites; D002846:Chromatography, Affinity; D004259:DNA-Directed DNA Polymerase; D015967:Gene Expression Regulation, Viral; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D012808:Sigma Factor; D015534:Trans-Activators; D014764:Viral Proteins; C085859:gene 33 protein, Enterobacteria phage T4; C069983:gene 43 protein, Enterobacteria phage T4; C074555:gene 45 protein, Enterobacteria phage T4; C106892:gene 55 protein, Enterobacteria phage T4; D004259:DNA-Directed DNA Polymerase; D000409:Alanine