Single-specific primer PCR was used to isolate a mouse-specific PMCA4 fragment, from which the entire cDNA was ultimately defined. A 5kb immediate upstream region of the PMCA4 locus was also isolated, and two putative transcriptional start sites were identified by primer extension. Promoter-luciferase reporter gene assays showed cell cycle-dependent repression in PMCA4 promoter, which was affected in part by c-Myb gene transfection. Alternative splicing at the amino and carboxy termini (sites A and C respectively) appeared to be regulated in a tissue-specific manner. Real-time RT-PCR revealed regulated expression of PMCA4-A and -C splice variants in response to cell cycle progression and depletion of intracellular Ca2+.PMCA4 is one of four members of the plasma membrane calcium ATPase family (PMCA1--4) of Ca2+ pumps, which serve to reduce intracellular Ca2+ concentrations. A splice variant, PMCA4CI, has a PDZ binding domain that also mediates protein-protein interactions with other PDZ domain-containing proteins, Over-expression of human PMCA4CI in vascular smooth cells (VSMC) of transgenic mice has been shown to increase blood pressure by decreasing the activity of neuronal nitric oxide synthase.