Neuronal cell type-specific promoter of the α CaM kinase II gene is activated by Zic2, a Zic family zinc finger protein

To understand the neuronal cell type-specific expression of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II), we investigated binding proteins that specifically activated the promoter of the α isoform of CaM kinase II (α CaM kinase II). Proteins that bind the promoter sequence were found in rat brain nuclear extract by electrophoretic mobility shift assay. Then, we screened for binding proteins in a mouse brain cDNA library using the yeast one-hybrid system. Zic2, a Zic family zinc finger transcription factor, was identified as one of the binding proteins. To investigate the effect of Zic2 on the promoter activity, Zic2 cDNA was expressed with a luciferase reporter gene containing a neuronal cell type-specific promoter of α CaM kinase II in neuronal and non-neuronal cells. The promoter activity of α CaM kinase II was enhanced 1.3-5-fold in cultured neuronal cells by Zic2. The activation was varied among neuronal cell types. Zic2 also increased the promoter activity in non-neuronal cells, although the relative luciferase activites in non-neuronal cells were lower than those in neuronal cell lines. These results indicated that Zic2 was one of the proteins binding to, and regulating the activity of, the promoter of α CaM kinase II.