AUTOREGULATION OF THE GENE ENCODING THE REPLICATION TERMINATOR PROTEIN OF BACILLUS-SUBTILIS

One of two putative sigma(A) promoters identified previously in the re gion immediately upstream from the rtp gene (encoding the replication terminator protein) [Smith and Wake, J. Bacteriol. 170 (1988) 4083-409 0] has been shown by transcription start point (tsp) mapping to be the functional rtp promoter. In these tsp mapping experiments, it was obs erved that the level of mRNA from this promoter, Prtp, was increased b y a factor of 30 in the absence of the replication terminator protein (RTP), consistent with the autoregulation of rtp at the level of trans cription. In vitro transcription from Prtp by sigma(A) RNA polymerase has been shown to be specifically repressed by RTP. A Prtp-spoVG-lacZ fusion was inserted into the chromosome of a strain in which RTP produ ction was inducible by IPTG. Addition of IPTG to cultures of the new s train lowered betaGal production by a factor of at least four. It is c oncluded that rtp is autoregulated in vivo at the level of transcripti on.