A novel light- and heat-responsive regulation of the groE transcription in the absence of HrcA or CIRCE in cyanobacteria.
The inactivation of the hrcA gene resulted in de-repression of the two CIRCE-containing groE genes in a cyanobacterium Synechocystis sp. strain PCC6803, indicating that the CIRCE operator/HrcA repressor system operates in the cyanobacterium. We found that the groE expression in the hrcA mutant is greatly induced by heat and/or light. Removal of a K-box containing and an N-box containing region upstream of the groESL1 promoter abolished light-induced transcription of a luxAB reporter gene fused with the groESL1 promoter. Similar sequences to the K-box, GTTCGG-NNAN-CCNNAC, were also found upstream of the dnaK2 genes. A specific binding of a protein(s) to the N-box, GATCTA, was detected by a gel mobility shift assay with using cell extracts. We propose that the cyanobacterial groEL expression is regulated by a putative positive mechanism mediated by these novel elements in addition to the HrcA/CIRCE system. The groEL2 genes from Synechococcus sp. strain PCC 7942 and Thermosynechococcus elongatus, which lack CIRCE, K-box, and N-box naturally, were also induced by heat and/or light, indicating that the control mechanism of the unique light-responsive groE expression is highly diversified in cyanobacteria.
Kojima
Kouji
K
Department of Biochemistry and Molecular Biology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
Nakamoto
Hitoshi
H
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D018834:Chaperonin 60 / Q000235:genetics; D018833:Chaperonins / Q000235:genetics*; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006358:Hot Temperature; D008027:Light; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D050436:Regulatory Elements, Transcriptional / Q000502:physiology; D012689:Sequence Homology, Nucleic Acid; D046939:Synechocystis / Q000235:genetics; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D018834:Chaperonin 60; C097970:GroESL protein, Bacteria; D018833:Chaperonins