title: Negative control of the high light-inducible hliA gene and implications for the activities of the NblS sensor kinase in the cyanobacterium Synechococcus elongatus strain PCC 7942.
abstract: The hliA gene of the cyanobacterium Synechococcus elongatus PCC 7942 is known to be upregulated by high-intensity light through the activity of the NblS sensor kinase. In this work it was found that, within the hliA upstream region, changes to the sequence around -30 to -25 (relative to the transcriptional start site) resulted in elevated hliA expression, implicating this region in negative regulation of the gene. Electrophoretic mobility shift assays performed were consistent with a protein binding this region that acts to keep the gene off in lower light. A reduction in gene dosage of nblS in vivo resulted in enhanced hliA expression, suggesting that negative control of hliA is mediated through NblS. An extended version of the high light regulatory 1 (HLR1) motif (previously described in Synechocystis PCC 6803) was identified within the sequence surrounding -30 to -25 of hliA. The extended HLR1 sequence was found upstream of other NblS-controlled genes from S. elongatus and Synechocystis PCC 6803 and upstream of hli genes from a variety of cyanobacterial and related genomes. These results point to the evolutionary conservation of the HLR1 element and its importance in NblS-mediated signaling and yield new insight into NblS-mediated control of gene expression.
authors.affiliation: Department of Biology, The University of Texas at Arlington, Arlington, TX 76019, USA.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Kappell
authors.forename: Devaki
authors.initials: D
authors.lastname: Bhaya
authors.forename: Lorraine G
authors.initials: LG
authors.lastname: van Waasbergen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D046940:Synechococcus / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; C091582:high light-inducible protein, cyanobacteria; D011494:Protein Kinases