%0 Electronic Article
%A Ge, Yong and Zhao, Ni and Hu, Xiaomin and Shi, Tingyu and Cai, Quanxin and Yuan, Zhiming
%I American Society for Microbiology
%D 2014
%D 2014
%G English
%@ 0021-9193
%@ 1098-5530
%~ Katalog der Westsächsischen Hochschule Zwickau
%T A Novel Transcriptional Activator, tubX , Is Required for the Stability of Bacillus sphaericus Mosquitocidal Plasmid pBsph
%V 196
%J Journal of Bacteriology
%V 196
%N 24
%P 4304-4314
%U http://dx.doi.org/10.1128/jb.01855-14
%X ABSTRACT
Stable maintenance of the low-copy-number plasmid pBsph in
Bacillus sphaericus
requires a partitioning (
par
) system that consists of a filament-forming protein,
B. sphaericus
TubZ (TubZ-Bs); a centromere-binding protein, TubR-Bs; and a centromere-like DNA site,
tubC
, composed of three blocks (I, II, and III) of 12-bp degenerate repeats. Previous studies have shown that mini-pBsph replicons encoding the TubZ system are segregationally highly unstable, whereas the native pBsph is stably maintained. However, the mechanism underlying the stability discrepancy between pBsph and its minireplicon is poorly understood. Here
orf187
(encoding TubX), a gene downstream of
tubZ
-Bs, was found to play a role in plasmid stabilization. Null mutation or overexpression of
tubX
resulted in a defect in pBsph stability and a significant decrease in the level of
tubRZ
-Bs expression, and the TubX-null phenotype was suppressed by ectopic expression of a wild-type copy of
tubX
and additional
tubRZ
-Bs. An electrophoresis mobility shift assay (EMSA) and a DNase I footprinting assay revealed that the TubX protein bound directly to five 8-bp degenerate repeats located in the
par
promoter region and that TubX competed with TubR-Bs for binding to the
par
promoter. Further studies demonstrated that TubX significantly stimulated the transcription of the
par
operon in the absence of
tubR
-Bs, and a higher level of gene activation was observed when
tubR
-Bs was present. These results suggested that TubX positively regulates
tubRZ
-Bs transcription by interfering with TubR-Bs-mediated repression and binding directly to the
tubRZ
-Bs promoter region.
%Z https://www.katalog.fh-zwickau.de/Record/ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMTEyOC9qYi4wMTg1NS0xNA
%U https://www.katalog.fh-zwickau.de/Record/ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMTEyOC9qYi4wMTg1NS0xNA