Light-responsive psbA transcription requires the -35 hexamer in the promoter and its proximal upstream element, UPE, in cyanobacteria.
We characterized the function of the -35 hexamer in the promoter and an element just upstream, UPE, in the expression in a unicellular cyanobacterium, Microcystis aeruginosa K-81, of the light-responsive gene psbA2, which encodes a reaction center key protein for photosynthesis. A series of mutants with mutations at the -35 hexamer (-35 to -30) and a novel conserved upstream element (UPE: -45 to -36, +1 referring to the transcription start point) were constructed. Expression of the mutants was examined in vivo and in vitro by analyses using a beta-galactosidase assay, primer extension, and a DNA-mobility shift assay with RNA polymerases. Results indicated that the -35 hexamer and its proximal UPE act as effective cis-elements for the light-responsive and/or basal transcription, respectively. A model of the 5'-upstream region with cis- and possible trans-acting factors is presented for the psbA regulatory system.
Ito
Yoko
Y
Laboratory of Molecular Genetics, School of Agriculture, Ibaraki University, Ami, Inashiki, Ibaraki 300-0393, Japan.
Asayama
Munehiko
M
Shirai
Makoto
M
D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D000458:Cyanobacteria / Q000235:genetics*; D017931:DNA Primers; D005809:Genes, Regulator / Q000235:genetics*; D008027:Light; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D045332:Photosystem II Protein Complex / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic / Q000528:radiation effects*
D017931:DNA Primers; D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit