RpaB, another response regulator operating circadian clock-dependent transcriptional regulation in Synechococcus elongatus PCC 7942.
The circadian clock of cyanobacteria is composed of KaiA, KaiB, and KaiC proteins, and the SasA-RpaA two-component system has been implicated in the regulation of one of the output pathways of the clock. In this study, we show that another response regulator that is essential for viability, the RpaA paralog, RpaB, plays a central role in the transcriptional oscillation of clock-regulated genes. In vivo and in vitro analyses revealed that RpaB and not RpaA could specifically bind to the kaiBC promoter, possibly repressing transcription during subjective night. This suggested that binding may be terminated by RpaA to activate gene transcription during subjective day. Moreover, we found that rpoD6 and sigF2, which encode group-2 and group-3 σ factors for RNA polymerase, respectively, were also targets of the RpaAB system, suggesting that a specific group of σ factors can propagate genome-wide transcriptional oscillation. Our findings thus reveal a novel mechanism for a circadian output pathway that is mediated by two paralogous response regulators.
Division of Applied Biological Chemistry, Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, Chiba 271-8510, Japan. mhanaoka@faculty.chiba-u.jp
Mitsumasa
M
Hanaoka
Naoki
N
Takai
Norimune
N
Hosokawa
Masayuki
M
Fujiwara
Yuki
Y
Akimoto
Nami
N
Kobori
Hideo
H
Iwasaki
Takao
T
Kondo
Kan
K
Tanaka
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D047369:Chromatin Immunoprecipitation; D057906:Circadian Clocks; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D060888:Real-Time Polymerase Chain Reaction; D046940:Synechococcus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; D014157:Transcription Factors