Identification and analysis of the promoter region of the human PLC-δ4 gene

The δ4 isoform of phospholipase C (PLC-δ4) is thought to be associated with various cellular functions and disease status. However, little is known about how its function is controlled in cells, particularly in terms of the regulation of its expression. To understand the regulation mechanisms of the PLC-δ4 gene transcription, the 5′-flanking region (-2046 ∼ +5) (the nucleotide sequence data reported in this paper have been submitted to the EMBL/GenBank/DDBJ data bank under accession numbers DQ302751) of the human PLC-δ4 gene was isolated from human genomic DNA. It was a TATA-less promoter with very GC-rich sequences near the transcription start site. The activity of the PLC-δ4 promoter was shown in various human and mouse cell lines by luciferase reporter assay. Serial deletion analysis identified the core promoter region as being between -402 and -67, in which an E-box and an AP-1 binding site played important roles in the promoter activity. In addition, we also showed that 12-O-tetradecanoylphorbol-1,3-acetate (TPA), a PKC activator and tumor promoter, induced the activity of the PLC-δ4 promoter via the AP-1 binding site. In summary, this study identified a core promoter region of the hPLC-δ4 gene and the factor binding sites responsible for the promoter activity. These results will provide important new information to further understand the regulatory mechanism of the PLC-δ4 function.