Structure, promoter analysis, and chromosomal localization of the murine H+/K+-ATPase alpha 2 subunit gene

The H+/K+-ATPase alpha2 subunit (HK alpha2) of distal colon and renal colle cting ducts plays a critical role in potassium and acid-base homeostasis. T he isolation and complete sequence of the murine HK alpha2 gene are reporte d. The HK alpha2 gene contains 23 exons and spans 23.5 kb of genomic DNA. T he exon/intron organization is comparable to that of the human ATP1AL1 gene . Primer extension and 5'-rapid amplification of cDNA ends of distal colon RNA were used to map the transcription initiation site. Fluorescence in sit u hybridization analysis localized the HK alpha2 gene to murine chromosome 14C3. Sequence analysis of 7.2 kb of the 5'-flanking region revealed numero us consensus sites for transcription factors, including two potential gluco corticoid response elements. Transient transfection of promoter-luciferase constructs demonstrated strong basal HK alpha2 promoter activity in renal c ollecting duct cells but not in fibroblasts or in a medullary thick ascendi ng limb of Hente's loop cell line. Deletion analysis revealed that the prox imal 0.2 kb of the promoter was sufficient to confer activity in collecting duct cells. These data should prove important in elucidation of the mechan isms controlling the differential, tissue-specific expression of the HK alp ha2 gene.