title: Comparative genomics analysis of NtcA regulons in cyanobacteria: regulation of nitrogen assimilation and its coupling to photosynthesis.
abstract: We have developed a new method for prediction of cis-regulatory binding sites and applied it to predicting NtcA regulated genes in cyanobacteria. The algorithm rigorously utilizes concurrence information of multiple binding sites in the upstream region of a gene and that in the upstream regions of its orthologues in related genomes. A probabilistic model was developed for the evaluation of prediction reliability so that the prediction false positive rate could be well controlled. Using this method, we have predicted multiple new members of the NtcA regulons in nine sequenced cyanobacterial genomes, and showed that the false positive rates of the predictions have been reduced on an average of 40-fold compared to the conventional methods. A detailed analysis of the predictions in each genome showed that a significant portion of our predictions are consistent with previously published results about individual genes. Intriguingly, NtcA promoters are found for many genes involved in various stages of photosynthesis. Although photosynthesis is known to be tightly coordinated with nitrogen assimilation, very little is known about the underlying mechanism. We postulate for the fist time that these genes serve as the regulatory points to orchestrate these two important processes in a cyanobacterial cell.
authors.affiliation: Bioinformatics Institute and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Zhengchang
authors.initials: Z
authors.lastname: Su
authors.forename: Victor
authors.initials: V
authors.lastname: Olman
authors.forename: Fenglou
authors.initials: F
authors.lastname: Mao
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D016384:Consensus Sequence; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023281:Genomics / Q000379:methods*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D018085:Regulon; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D009584:Nitrogen