Back to Search Start Over

Promoters for Chlamydia type III secretion genes show a differential response to DNA supercoiling that correlates with temporal expression pattern

Authors :
Case, Elizabeth Di Russo
Peterson, Ellena M.
Tan, Ming
Source :
Journal of Bacteriology. May, 2010, Vol. 192 Issue 9-10, p2569, 6 p.
Publication Year :
2010

Abstract

Type III secretion (T3S) is important for the establishment and maintenance of a chlamydial infection. The genes encoding T3S components in Chlamydia are transcribed as separate temporal classes, but the mechanisms that regulate the timing of their expression are not understood. In this study, we demonstrate that promoters for 10 predicted T3S transcriptional units are each transcribed in vitro by the major form of chlamydial RNA polymerase but not by an alternative form of RNA polymerase containing [[sigma].sup.28]. Since changes in DNA supercoiling during chlamydial development have been proposed as a mechanism for temporal gene regulation, we examined the in vitro response of T3S promoters to altered superhelical density. Promoters for three T3S genes that are upregulated at mid times were activated in response to increased DNA supercoiling. In contrast, promoters for three late T3S genes were not sensitive to changes in superhelical density. This differential response to changes in DNA topology is similar to the pattern that has been reported for representative mid and late chlamydial genes that are unrelated to the T3S system. Based on these results, we propose that the temporal expression of T3S genes in Chlamydia is controlled by general mechanisms that regulate [[sigma].sup.66]-dependent gene expression during the developmental cycle. Our results are consistent with a model in which T3S genes that are upregulated in mid cycle are activated together with other mid genes in response to increased DNA supercoiling. doi: 10.1128/JB.00068-10

Details

Language :
English
ISSN :
00219193
Volume :
192
Issue :
9-10
Database :
Gale General OneFile
Journal :
Journal of Bacteriology
Publication Type :
Academic Journal
Accession number :
edsgcl.227651839