A direct interaction between a DNA-tracking protein and a promoter recognition protein: implications for searching DNA sequence.
Bacteriophage T4 gene 45 protein, gp45, serves as the sliding clamp of viral DNA replication and as the activator of T4 late gene transcription. In the latter context, DNA tracking is an essential feature of the unique mechanism of action. T4 late promoters, which consist of a simple TATA box, TATAAATA, are recognized by the small sigma-family gene 55 protein, gp55, which binds to Escherichia coli RNA polymerase core. A direct and RNA polymerase-independent interaction of gp45 with gp55 has been demonstrated in two ways. (i) gp45 tracks along DNA; co-tracking of gp55 requires the previously documented DNA-loading process of gp45, and can be detected by photochemical crosslinking. (ii) The dynamics of DNA tracking by gp45 can be followed by footprinting; the catenated DNA-tracking state of gp45 is short-lived, but is stabilized by gp55. The ability of this topologically linked DNA-tracking transcriptional activator to interact directly with a promoter recognition protein suggests the existence of multiple pathways of promoter location, which are discussed.
Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla 92093-0634, USA.
R L
RL
Tinker-Kulberg
T J
TJ
Fu
E P
EP
Geiduschek
G A
GA
Kassavetis
D001426:Bacterial Proteins; D004247:DNA / Q000378:metabolism*; D018983:DNA Footprinting; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D029968:Escherichia coli Proteins; D011401:Promoter Regions, Genetic; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013604:T-Phages / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D015534:Trans-Activators; D014764:Viral Proteins; C074555:gene 45 protein, Enterobacteria phage T4; D004247:DNA; C490362:NrdG protein, E coli; D012264:Ribonucleotide Reductases; C490361:nrdG protein, Enterobacteria phage T4; C090389:nrdG protein, bacteria; D004259:DNA-Directed DNA Polymerase