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Originally published in Science Express on 18 November 2004
Science 14 January 2005:
Vol. 307. no. 5707, pp. 251 - 254
DOI: 10.1126/science.1102540
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Reports

No Transcription-Translation Feedback in Circadian Rhythm of KaiC Phosphorylation

Jun Tomita, Masato Nakajima, Takao Kondo, Hideo Iwasaki*

An autoregulatory transcription-translation feedback loop is thought to be essential in generating circadian rhythms in any model organism. In the cyanobacterium Synechococcus elongatus, the essential clock protein KaiC is proposed to form this type of transcriptional negative feedback. Nevertheless, we demonstrate here temperature-compensated, robust circadian cycling of KaiC phosphorylation even without kaiBC messenger RNA accumulation under continuous dark conditions. This rhythm persisted in the presence of a transcription or translation inhibitor. Moreover, kinetic profiles in the ratio of KaiC autophosphorylation-dephosphorylation were also temperature compensated in vitro. Thus, the cyanobacterial clock can keep time independent of de novo transcription and translation processes.

Division of Biological Science, Graduate School of Science, Nagoya University, and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.

* To whom correspondence should be addressed. E-mail: iwasaki{at}bio.nagoya-u.ac.jp

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Science. ISSN 0036-8075 (print), 1095-9203 (online)