Transcriptional activation by a DNA-tracking protein: structural consequences of enhancement at the T4 late promoter.
Transcriptional initiation at bacteriophage T4 late promoters is activated from enhancer-like distal sites by the T4 gene 44, 62, and 45 DNA polymerase accessory proteins (gp44, gp62, and gp45, respectively). Enhancement is ATP hydrolysis-dependent and requires protein tracking along DNA. The structural analysis of the enhanced transcription initiation complex shows gp45 located at the upstream end of this promoter complex in the vicinity of its transcriptional coactivator, the T4 gene 33 protein. The ATP-cleaving gene 44 protein-gene 62 protein complex serves as the assembly factor for gp45, but does not stably associate with the enhanced promoter complex. Transcriptional enhancement quantitatively favors, but does not qualitatively change, DNA strand separation in the transcription bubble. A model of the transcriptional activation that rationalizes its DNA-tracking and activation-polarity properties is presented.
Tinker
R L
RL
Department of Biology, University of California, San Diego, La Jolla 92093-0634.
Williams
K P
KP
Kassavetis
G A
GA
Geiduschek
E P
EP
D000255:Adenosine Triphosphate / Q000378:metabolism; D017122:Bacteriophage T4 / Q000235:genetics*; D001483:Base Sequence; D003432:Cross-Linking Reagents; D015342:DNA Probes; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics; D006023:Glycoproteins / Q000096:biosynthesis; D006868:Hydrolysis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D012808:Sigma Factor / Q000378:metabolism; D015533:Transcriptional Activation
D003432:Cross-Linking Reagents; D015342:DNA Probes; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D006023:Glycoproteins; D012333:RNA, Messenger; D012808:Sigma Factor; D000255:Adenosine Triphosphate; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases