While cyclin-dependent kinases, such as CDC2 and CDK2, are key regulators of cell-cycle progression, cyclin-dependent kinase 5 (CDK5) is highly expressed in mature neurons with no evident cell-cycle regulation. The 5'-region of the mouse CDK5 gene was isolated and sequenced. The isolated clone included exons 1 through 7. The 5'-flanking region has a high G+C content. There is no TATA box around the transcriptional start points (tsp), as determined by primer extension analysis. One CCAAT box, one AP-1-binding site, two AP-2-binding sites, and one cAMP-responsive element are located upstream from the tsp. Promoter/cat fusion assays showed that the 5.8-kb fragment of this 5'-flanking sequence possessed the promoter activities expressing cat in rat PC12 pheochromocytoma cells. The effect of deletions of the promoter suggested the presence of two negative control elements located from -2.9 kb to -546 bp, and from -212 to -155 upstream from the 5' end of the tsp. Two positive elements from bp -300 to -212 and from -155 to -41 were also detected. In the element from bp -300 to -212, there was a putative NF-IL6-binding sequence. Thus, the CDK5 promoter region contains multiple positive and negative cis-acting regulatory elements, an arrangement which suggests that the regulation of transcription of CDK5 is under complex control.