IN-VIVO ROLES OF BM3R1 REPRESSOR IN THE BARBITURATE-MEDIATED INDUCTION OF THE CYTOCHROME-P450 GENES (P450(BM-3) AND P450(BM-1)) OF BACILLUS-MEGATERIUM

We previously showed [Q. Liang, A.J. Fulco, J. Biol. Chem., 270 (1995) 18606-18614) that the binding of Bm3R1 repressor to Barbie box elemen ts and operator sites in the 5'-flanking regions of the P450(BM-3), an d P450(BM-1), (CYP102 and CYP106) genes in Bacillus megaterium was a c ritical factor in their regulation at the level of transcription. We n ow describe experiments that delineate specific roles for Bm3R1 in the barbiturate-mediated induction of these genes. We directly demonstrat e the interaction of Bm3R1 with Barbie box and operator sequences and show that high in vivo levels of Bm3R1 prevent putative positive facto rs from binding to Barbie box elements, strongly inhibit the expressio n of the P450 genes, prolong the lag phase of growth in Bacillus megat erium cultures and increase the sensitivity of the cells to the growth -inhibitory effects of barbiturates. Finally, our data suggest that th ere may be two forms of Bm3R1, either of which can interact with O-III , the bicistronic operator sequence. (C) 1998 Elsevier Science B.V.