title: Deletion mutagenesis of the 5' psbA2 region in Synechocystis 6803: identification of a putative cis element involved in photoregulation.
abstract: Three Synechocystis 6803 mutants, with deletions in the upstream region of the light-regulated psbA2 gene, were constructed. All three mutants grew photoautotrophically but they were affected in psbA2 expression. In one of the mutants, DeltaU80, psbA2 transcription levels were not suppressed under low light conditions and production of psbA2 transcripts occurred also in darkness, in contrast to the situation in the control strain. Comparative sequence analyses of the mutants identified a hexanucleotide repeat as possible cis element in psbA2 light regulation. Electrophoresis mobility shift assays showed that protein binding to the hexanucleotide repeat decreased with light intensity, consistent with a hypothesis that the repeat harbors a binding site for a repressor protein. Repeats similar to that in psbA2 were found also in the upstream region of other light-regulated genes in Synechocystsis 6803. We refer to these hexanucleotide repeats as High Light Regulatory 1 (HLR1) sequences.
authors.affiliation: Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala, S-75007, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Eriksson
authors.forename: G F
authors.initials: GF
authors.lastname: Salih
authors.forename: H
authors.initials: H
authors.lastname: Ghebramedhin
authors.forename: C
authors.initials: C
authors.lastname: Jansson
mesh_terms: D001483:Base Sequence; D000458:Cyanobacteria / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045332:Photosystem II Protein Complex; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012329:RNA, Bacterial / Q000032:analysis; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D012329:RNA, Bacterial