William R. McClure
625A Mellon Institute
Department of Biological Sciences
Carnegie Mellon University
4400 Fifth Avenue
Pittsburgh, PA 15213
Ph.D., University of Wisconsin
Postdoctoral Appointment, Max Planck Institute
The interaction of E. coli RNA polymerase with several bacterial promoters has been investigated in vitro with experiments that focus on the rate limiting steps in RNA chain initiation. We have developed a sensitive and versatile assay that separately quantifies the initial binding of the enzyme to the promoter and the subsequent isomerization steps in the initiation reaction. The mechanistic studies relating to initiation frequency include the characterization of the effect of promoter mutations, activators, repressors and DNA supercoiling on the rate limiting steps.
Mutations in the s subunit of RNA polymerase are being characterized that alter the promoter recognition steps in transcription initiation. These studies are expected to define the regions of the enzyme that are responsible for contacting conserved sequences in the promoter. Other s mutations appear to alter intermediates on the pathway of the initiation process; these are being characterized with chemical and enzymatic protection techniques.
In two bacteriophage systems, we have found that the synthesis of an antisense RNA is an important contribution to the control of gene expression. Bacteriophage P22 encodes an antisense RNA in the sar gene that is responsible for the turn-off of an early gene function. The solution structure and pairing mechanism of SarRNA are studied with several biochemical approaches.
Li M, McClure WR and Susskind MM. Changing the mechanism of transcriptional activation by phage lambda repressor. Proceedings of the National Academy of Sciences USA, 1996.
Su TT and McClure WR. Selective binding of E. coli RNA polymerase to topoisomers of mini-circles carrying the TAC16 and TAC17 promoters. Journal of Biological Chemistry, 269:13511-13521, 1994.
Goodrich JA and McClure WR. Regulation of open complex formation at the E. coli galactose operon promoters: Simultaneous interaction of RNA polymerase, gal repressor, and CAP/cAMP. Journal of Molecular Biology, 224:15-29, 1992.
Goodrich JA and McClure WR. Competing promoters in prokaryotes. Trends in Biochemical Sciences, 16:394-397, 1991.