TRANSCRIPTION-REPAIR COUPLING FACTOR IS INVOLVED IN CARBON CATABOLITEREPRESSION OF THE BACILLUS-SUBTILIS HUT AND GNT OPERONS

A Bacilius subtilis mutant that partially relieves carbon catabolite r epression (CCR) of the hut operon was isolated by transposon mutagenes is. Characterization of this mutant revealed that the transposon had i nserted into the gene, mfd, that encodes transcription-repair coupling factor. The Mfd protein is known to promote strand-specific DNA repai r by displacing RNA polymerase stalled at a nucleotide lesion and dire cting the (A)BC excinuclease to the RNA damage site. A set of transcri ptional lacZ fusions was used to demonstrate that the mfd mutation rel ieves CCR of hut and gnt expression at the cis-acting ore sequences lo cated downstream of the transcriptional start site but does not affect CCR at sites located at the promoters. CCR of the amyE and bglPH gene s, which contain ore sequences that overlap their promoters, is not al tered by the mfd mutation. These results support a model in which the Mfd protein displaces RNA polymerase stalled at downstream ore sites t hat function as transcriptional roadblocks and reveal a new role for M fd in cellular physiology.