MSystems: Identification of a GrgA-Euo-HrcA Transcriptional Regulatory Network in Chlamydia (Lai Lab)

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Wurihan Wurihan , Yi ZouAlec M. WeberKorri WeldonYehong Huang, Xiaofeng BaoChengsheng ZhuXiang WuYaqun WangZhao Lai, and Huizhou Fan 

ABSTRACT

Chlamydia trachomatis is an obligate intracellular bacterium whose unique developmental cycle consists of an infectious elementary body and a replicative reticulate body. Progression of this developmental cycle requires temporal control of the transcriptome. In addition to the three chlamydial sigma factors (σ66, σ28, and σ54) that recognize promoter sequences of genes, chlamydial transcription factors are expected to play crucial roles in transcriptional regulation. Here, we investigate the function of GrgA, a Chlamydiaspecific transcription factor, in C. trachomatis transcriptomic expression. We show that 10 to 30 min of GrgA overexpression induces 13 genes, which likely comprise the direct regulon of GrgA. Significantly, σ66-dependent genes that code for two important transcription repressors are components of the direct regulon. One of these repressors is Euo, which prevents the expression of late genes during early phases. The other is HrcA, which regulates molecular chaperone expression and controls stress response. The direct regulon also includes a σ28-dependent gene that codes for the putative virulence factor PmpI. Furthermore, overexpression of GrgA leads to decreased expression of almost all tRNAs. Transcriptomic studies suggest that GrgA, Euo, and HrcA have distinct but overlapping indirect regulons. These findings, together with temporal expression patterns of grgAeuo, and hrcA, indicate that a transcriptional regulatory network of these three transcription factors plays critical roles in C. trachomatis growth and development.

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Article Categories: Research Paper