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J Biol Chem. 1995 Jun 30;270(26):15899-907.

The COOH-terminal domain of the RNA polymerase alpha subunit in transcriptional enhancement and deactivation at the bacteriophage T4 late promoter.

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Department of Biology, University of California, San Diego 92093-0634, USA.


Many activator proteins generate their positive control of transcription through interactions with the COOH-terminal domain of the Escherichia coli RNA polymerase alpha subunit. We have examined the participation of this alpha-domain in transcriptional enhancement and suppression at bacteriophage T4 late promoters. Enhancement is generated by the T4 gene 45 protein, which is the DNA-tracking processivity factor of viral DNA replication; suppression of unenhanced transcription is generated by the RNA polymerase-binding co-activator T4 gene 33 protein. Enhanced and unenhanced transcription by RNA polymerase reconstituted with intact and truncated alpha subunits and by RNA polymerase containing ADP-ribosylated alpha has been compared; the internal structures of transcription complexes formed with these RNA polymerases have also been analyzed by footprinting and photocross-linking. Comparison of these structural and functional analyses suggests that enhancement of T4 late transcription by gp45 is not compatible with any significant role of the COOH-terminal domain of the RNA polymerase core alpha subunit in transcriptional initiation. Suppression of unenhanced T4 late transcription by the gene 33 protein also does not require the COOH-terminal domain of alpha.

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