title: Repression of transcription initiation at 434 P(R) by 434 repressor: effects on transition of a closed to an open promoter complex.
abstract: The lambdoid bacteriophage repressors function both as transcription activators and repressors. Regulation of transcription at the adjacent, but divergent promoters, P(RM) and P(R), determines the phage's choice between the lytic and lysogenic development pathways. Here, we demonstrate that 434 repressor bound at 434 O(R)1 alone is not sufficient to repress transcription from 434 P(R,) but that 434 repressor bound at 434 O(R)2 alone is necessary and sufficient to repress P(R )transcription. This is different from what occurs in the related bacteriophage lambda, in which binding of lambda repressor to either lambdaO(R)1 or lambdaO(R)2 represses transcription from lambdaP(R). The combined results of gel mobility shift and KMnO(4) footprinting assays show that while 434 repressor binding to 434 O(R)2 does not preclude RNA polymerase binding at the P(R) promoter, it does prevent it from forming open complexes at this promoter. The RNA polymerase-P(R) complexes that form in the presence of repressor are heparin-resistant and the DNA is not melted. This observation indicates that 434 repressor bound at 434 O(R)2 inhibits transcription initiation at the P(R) promoter by "locking" the RNA polymerase-P(R) complex into an inactive state instead of "blocking" the access of RNA polymerase to promoter DNA.
authors.affiliation: Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260, USA.
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: G B
authors.initials: GB
authors.lastname: Koudelka
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018983:DNA Footprinting; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000821:virology; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D005814:Genes, Viral / Q000235:genetics; D006493:Heparin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation / Q000187:drug effects; D011196:Potassium Permanganate / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D013698:Templates, Genetic; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D014764:Viral Proteins
chemical_list: C063367:434-repressor protein, Bacteriophage 434; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D011196:Potassium Permanganate; D006493:Heparin; D012321:DNA-Directed RNA Polymerases; D003850:Deoxyribonuclease I