To date, little is known about the molecular mechanisms controlling the regulation of phospholipase C-delta 1 (PLC-delta 1) gene expression. To understand the mechanisms responsible for the regulation of PLC-delta 1 gene expression, the 5'-flanking region of the mouse PLC-delta 1 gene was isolated from a mouse genomic DNA library. Primer extension analysis revealed that there is a single transcriptional start site located at 127 bases upstream from the translation start codon in the mouse PLC-delta 1 gene. DNA sequence analysis showed that the sequence around the transcriptional start site is very GC-rich and has no TATA or CAAT boxes. Transient expression of a luciferase reporter gene under the control of serially deleted 5'-flanking sequences revealed that the 160-base-pair region from -622 to -462 upstream of the transcriptional start site includes a positive cis-acting element(s) for the efficient expression of the PLC-delta 1 gene. Gel retardation analysis suggests that multiple transcription factors bind to separate sites on the promoter region. Based on these results, our study suggests that the minimal essential region located at -622 to +70 is fully sufficient to confer high-level transcriptional activity and contains high-affinity binding elements for multiple transcription factors.