Previous Article | Next Article ![]()
J. Bacteriol., Feb 1996, 840-845, Vol 178, No. 3
CF Yang, JM Kim, E Molinari and S DasSarma
The bop gene of wild-type Halobacterium halobium NRC-1 is transcriptionally
induced more than 20-fold under microaerobic conditions. bop transcription
is inhibited by novobiocin, a DNA gyrase inhibitor, at concentrations
subinhibitory for growth. The exposure of NRC-1 cultures to novobiocin
concentrations inhibiting bop transcription was found to partially relax
plasmid DNA supercoiling, indicating the requirement of high DNA
supercoiling for bop transcription. Next, the bop promoter region was
cloned on an H. halobium plasmid vector and introduced into NRC-1 and S9, a
bop overproducer strain. The cloned promoter was active in both H. halobium
strains, but at a higher level in the overproducer than in the wild type.
Transcription from the bop promoter on the plasmid was found to be
inhibited by novobiocin to a similar extent as was transcription from the
chromosome. When the cloned promoter was introduced into S9 mutant strains
with insertions in either of two putative regulatory genes, brp and bat, no
transcription was detectable, indicating that these genes serve to activate
transcription from the bop promoter in trans. Deletion analysis of the
cloned bop promoter from a site approximately 480 bp upstream of bop showed
that a 53-bp region 5' to the transcription start site is sufficient for
transcription, but a 28- bp region is not. An 11-bp alternating
purine-pyrimidine sequence within the functional promoter region, centered
23 bp 5' to the transcription start point, was found to display DNA
supercoiling- dependent sensitivity to S1 nuclease and OsO4, which is
consistent with a non-B-DNA conformation similar to that of left-handed
Z-DNA and suggests the involvement of unusual DNA structure in
supercoiling- stimulated bop gene transcription.
Copyright © 1996, American Society for Microbiology
Genetic and topological analyses of the bop promoter of Halobacterium halobium: stimulation by DNA supercoiling and non-B-DNA structure
Department of Microbiology, University of Massachusetts, Amherst 01003, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»