title: Cross-talk and regulatory interactions between the essential response regulator RpaB and cyanobacterial circadian clock output.
abstract: The response regulator RpaB (regulator of phycobilisome associated B), part of an essential two-component system conserved in cyanobacteria that responds to multiple environmental signals, has recently been implicated in the control of cell dimensions and of circadian rhythms of gene expression in the model cyanobacterium Synechococcus elongatus PCC 7942. However, little is known of the molecular mechanisms that underlie RpaB functions. In this study we show that the regulation of phenotypes by RpaB is intimately connected with the activity of RpaA (regulator of phycobilisome associated A), the master regulator of circadian transcription patterns. RpaB affects RpaA activity both through control of gene expression, a function requiring an intact effector domain, and via altering RpaA phosphorylation, a function mediated through the N-terminal receiver domain of RpaB. Thus, both phosphorylation cross-talk and coregulation of target genes play a role in the genetic interactions between the RpaA and RpaB pathways. In addition, RpaB∼P levels appear critical for survival under light:dark cycles, conditions in which RpaB phosphorylation is environmentally driven independent of the circadian clock. We propose that the complex regulatory interactions between the essential and environmentally sensitive NblS-RpaB system and the SasA-RpaA clock output system integrate relevant extra- and intracellular signals to the circadian clock.
authors: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03080 Alicante, Spain; and Center for Circadian Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093.
authors: Javier
authors: J
authors: Espinosa
authors: Center for Circadian Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093.
authors: Joseph S
authors: JS
authors: Boyd
authors: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03080 Alicante, Spain; and.
authors: Raquel
authors: R
authors: Cantos
authors: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03080 Alicante, Spain; and.
authors: Paloma
authors: P
authors: Salinas
authors: Center for Circadian Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093 sgolden@ucsd.edu contrera@ua.es.
authors: Susan S
authors: SS
authors: Golden
authors: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03080 Alicante, Spain; and sgolden@ucsd.edu contrera@ua.es.
authors: Asuncion
authors: A
authors: Contreras
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D002940:Circadian Rhythm; D000458:Cyanobacteria / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D010766:Phosphorylation
chemical_list: D001426:Bacterial Proteins
keywords: chronobiology; signaling network; transcription regulation
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