Diversity of σ66-Specific Promoters Contributes to Regulation of Developmental Gene Expression in Chlamydia trachomatis

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Journal of Bacteriology


Promoter recognition by the RNA polymerase (RNAP) holoenzyme is a key step in gene regulation. In Chlamydia trachomatis, a medically important obligate intracellular bacterium, s66 allows the RNAP to initiate promoter-specific transcription throughout the chlamydial developmental cycle. Here, we investigated the intrinsic properties of s66-specific promoters with emphasis on their role in the developmental gene expression of C. trachomatis. First, we examined whether promoters that contain a 59-T(-15)G(-14)-39 (TG) motif upstream from the 210 element appear more often than others in genes that are preferentially expressed during the early, middle, or late stages of the C. trachomatis developmental cycle. We then determined the critical genetic elements that are required for transcription initiation in vitro. We also assessed the activity of promoters in the presence of Scc4, which can directly interact with s66RNAP. Finally, we evaluated the promoter-specific dynamics during C. trachomatis infection using a reporter assay. These results reveal that the TG motif is an important determinant in certain early or late promoters. The TG promoters that have the 235 element are recognized by s66RNAP and Scc4 differently from those lacking the 235 element. Based on these properties, the s66specific promoters can fall into three classes. Architectural diversity, behavioral plasticity, and the specific interplays between promoters and the s66RNAP likely contribute to developmental gene transcription in C. trachomatis. IMPORTANCE Meticulous promoter elucidation is required to understand the foundations of transcription initiation. However, knowledge of promoter-specific transcription remains limited in C. trachomatis. This work underscores the structural and functional plasticity of s66-specific promoters that are regulated by s66RNAP, as well as their importance in the developmental gene regulation of C. trachomatis.

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