THE COOH-TERMINAL DOMAIN OF THE RNA-POLYMERASE ALPHA-SUBUNIT IN TRANSCRIPTIONAL ENHANCEMENT AND DEACTIVATION AT THE BACTERIOPHAGE-T4 LATE PROMOTER

Many activator proteins generate their positive control of transcripti on through interactions with the COOH-terminal domain of the Escherich ia coli RNA polymerase alpha subunit. We have examined the participati on of this alpha-domain in transcriptional enhancement and suppression at bacteriophage T4 late promoters, Enhancement is generated by the T 4 gene 45 protein, which is the DNA-tracking processivity factor of vi ral DNA replication; suppression of unenhanced transcription is genera ted by the RNA polymerase-binding coactivator T4 gene 33 protein. Enha nced 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 tr anscription 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 lat e transcription by gp45 is not compatible with any significant role of the COOH-terminal domain of the RNA polymerase core a subunit in tran scriptional initiation. Suppression of unenhanced T4 late transcriptio n by the gene 33 protein also does not require the COOH-terminal domai n of alpha.