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Transcriptional regulation of the circadian clock operon kaiBC by upstream regions in cyanobacteria
Author(s) -
Kutsuna Shinsuke,
Nakahira Yoichi,
Katayama Mitsunori,
Ishiura Masahiro,
Kondo Takao
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04781.x
Subject(s) - biology , operon , transcription (linguistics) , primer extension , genetics , upstream activating sequence , circadian clock , circadian rhythm , promoter , coding region , gene , messenger rna , gene expression , mutant , linguistics , philosophy , neuroscience
Summary In the cyanobacterium, Synechococcus elongatus PCC 7942, the kaiBC operon is upregulated by the KaiA protein and downregulated by the KaiC protein to generate circadian oscillation. We investigated the regulation of kaiBC transcription. A primer extension and deletion analyses of the upstream region mapped the sufficient promoter region (SPR) to base pairs −55 to +1 (the transcription start site, TSS) and identified a constitutive negative regulatory region upstream of the SPR (base pairs −897 to −56) that extended into the coding sequence of kaiA . Base‐pair substitution within the SPR identified a sequence from −52 to −28 that was the essential element for transcription. Most of the examined sequences drove rhythmic expression of a luxAB reporter that was similar to the expression driven by the kaiBC promoter (P kaiBC ) and responded to the overexpression of kaiA or kaiC , even in a promoter activity range of 1–8000%. These results indicate that circadian feedback regulation by KaiA and KaiC is addressed to a global step preceding transcription driven by P kaiBC . However, increasing or decreasing the intrinsic activity of P kaiBC greatly affected the rhythm, suggesting that constitutive adjustment of P kaiBC activity by the sequences identified here is essential for the oscillator.