Promoter activity of the 5′-flanking regions of medaka fish soluble guanylate cyclase α₁ and β subunit genes

We examined the spatial expression pattern of medaka fish (Oryzias latipes) soluble guanylate cyclase α₁ and β₁ subunit genes, OlGCS-α₁ and OIGCS-β₁, and characterized the 5′-flanking region required for expression of both genes by introducing various promoter-luciferase fusion-gene constructs into COS-1 cells and medaka fish embryos. The OlGCS-α₁ and OIGCS-β₁ gene transcripts were detected in whole brain and kidney in 7-day and 9-day embryos. Primer-extension analysis demonstrated that there were no differences among various adult organs (brain, eye, kidney, ovary and testis) in the transcription start site of the OIGCS-α₁ and OIGCS-β₁ genes. Neither gene contained the functional TATA box within its 5′-flanking region, and the basal promoter activity was found between nucleotides +33 and +42 in the OIGCS-α₁ gene and between nucleotides + 146 and + 155 in the OIGCS-β₁ gene. In the assay of medaka fish embryos, the 5′-flanking region of the OIGCS-β₁ gene exhibited lower promoter activity than that of the OIGCS-α₁ gene. In the experiments on dual-luciferase fusion-gene constructs, the 5′-flanking region of the OIGCS-α₁ gene connected to the 5′-flanking region of the OIGCS-β₁ gene was introduced into medaka fish embryos, and the 5′-flanking regions of both subunit genes were shown to mutually influence each other's promoter activity.