Previously, we analyzed the promoter architecture of the psaAB genes encoding reaction center subunits of photosystem I (PSI) in the cyanobacterium Synechocystis sp. PCC 6803. There exist two promoters, P1 and P2, both of which show typical high-light (HL) response of PSI genes; their activities are high under low-light (LL) conditions but rapidly downregulated upon the shift to HL conditions. In this study, it was suggested that a response regulator RpaB binds to multiple high-light regulatory 1 (HLR1) sequences in the upstream region of the psaAB genes. We explored the regulatory role of cis-elements, including these HLR1 sequences on the individual activity of P1 and P2. Under LL conditions, the most influential cis-element is HLR1C (-62 to -45, relative to the transcriptional starting point of P1) working for positive regulation of P1. The other HLR1 sequences also affect the promoter activity under LL conditions; HLR1A (-255 to -238) is involved in repression of P1, whereas HLR1B (-153 to -126) works for activation of P2. Upon the shift to HL conditions, regulation via HNE2 located within the region from -271 to -177 becomes active in order to downregulate both P1 and P2 activities. A positive effect of HLR1B on P2 may persist under HL. These results suggest that cis-elements, including multiple HLR1 sequences, differently regulate the activities of dual promoters of the psaAB genes to achieve the fine-tuning of the gene expression. Copyright © 2010, American Society for Microbiology. All Rights Reserved.
CITATION STYLE
Takahashi, T., Nakai, N., Muramatsu, M., & Hihara, Y. (2010). Role of multiple HLR1 sequences in the regulation of the dual promoters of the psaAB genes in Synechocystis sp. PCC 6803. Journal of Bacteriology, 192(15), 4031–4036. https://doi.org/10.1128/JB.00444-10
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