Transcriptional activation of NtcA-dependent promoters of Synechococcus sp. PCC 7942 by 2-oxoglutarate invitro
- Ryohei Tanigawa*,
- Masao Shirokane*,
- Shin-ichi Maeda†,
- Tatsuo Omata†,
- Kan Tanaka*, and
- Hideo Takahashi*,‡
- *Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan; and †Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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Edited by Robert Haselkorn, Integrated Genomics, Inc., Chicago, IL, and approved January 28, 2002 (received for review November 2, 2001)
Abstract
The transcription factor NtcA is a global regulator of nitrogen homeostasis in cyanobacteria. It thus positively regulates the expression of genes related to nitrogen assimilation such as glnA (which encodes glutamine synthetase) and ntcA itself in response to nitrogen shortage or depletion. The binding of NtcA to the glnA and ntcA promoters of Synechococcus sp. PCC 7942 in vitro now has been shown to be enhanced by 2-oxoglutarate. In vitro analysis of gene transcription also revealed that the interaction of NtcA with its promoter element was not sufficient for activation of transcription, and 2-oxoglutarate was required for transcriptional initiation by NtcA. Given that the intracellular concentration of 2-oxoglutarate is inversely related to nitrogen availability, it is proposed that this metabolite functions as a signaling molecule that transmits information on cellular nitrogen status to NtcA and thereby regulates the transcription of genes related to nitrogen assimilation in cyanobacteria.
Footnotes
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↵ ‡ To whom reprint requests may be addressed. E-mail: htakaha{at}imcbns.iam.u-tokyo.ac.jp.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviations:
- GS,
- glutamine synthetase;
- GOGAT,
- glutamate synthase;
- 2-OG,
- 2-oxoglutarate;
- CRP,
- cAMP receptor protein;
- EMSA,
- electrophoretic mobility-shift assay
- Copyright © 2002, The National Academy of Sciences
