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  • Title: The bacteriophage T4 late-transcription coactivator gp33 binds the flap domain of Escherichia coli RNA polymerase.
    Author: Nechaev S, Kamali-Moghaddam M, André E, Léonetti JP, Geiduschek EP.
    Journal: Proc Natl Acad Sci U S A; 2004 Dec 14; 101(50):17365-70. PubMed ID: 15574501.
    Abstract:
    Transcription of bacteriophage T4 late genes requires concomitant DNA replication. T4 late promoters, which consist of a single 8-bp -10 motif, are recognized by a holoenzyme containing Escherichia coli RNA polymerase core and the T4-encoded promoter specificity subunit, gp55. Initiation of transcription at these promoters by gp55-holoenzyme is inefficient, but is greatly activated by the DNA-loaded DNA polymerase sliding clamp, gp45, and the coactivator, gp33. We report that gp33 attaches to the flap domain of the Escherichia coli RNA polymerase beta-subunit and that this interaction is essential for activation. The beta-flap also mediates recognition of -35 promoter motifs by binding to sigma(70) domain 4. The results suggest that gp33 is an analogue of sigma(70) domain 4 and that gp55 and gp33 together constitute two parts of the T4 late sigma. We propose a model for the role of the gp45 sliding clamp in activation of T4 late-gene transcription.
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