Characterization of the rabbit HKα2 gene promoter

The HKα2 gene directs synthesis of the HKα2 subunit of the H+, K+-ATPase. In the kidney and colon, the gene is highly expressed and is thought to play a role in potassium (K+) conservation. The rabbit has been an important experimental system for physiological studies of ion transport in the kidney, so the rabbit HKα2 gene has been cloned and characterized. The genomic clones and the previously reported HKα2a and HKα2c subunit cDNAs provided a means to address several issues regarding the structure and expression of the HKα2 gene. First, the genomic organization established that the rabbit HKα2 gene was unambiguously homologous to the mouse HKα2 gene and the human ATP1AL1 gene. Second, the mapping of the transcription start site for the alternate transcript, HKα2c, confirmed that it was an authentic rabbit transcript. Finally, isolation of DNA from the 5′ end of the HKα2 gene enabled us to initiate studies on its regulation in the rabbit cortical collecting duct. The promoter and two putative negative regulatory regions were identified and the effect of cell confluency on gene expression was studied.