Structure, Promoter Analysis, and Chromosomal Localization of the Murine H+/K+-ATPase α2 Subunit Gene

Abstract

ABSTRACT. The H+/K+-ATPase α2 subunit (HKα2) of distal colon and renal collecting ducts plays a critical role in potassium and acid-base homeostasis. The isolation and complete sequence of the murine HKα2 gene are reported. The HKα2 gene contains 23 exons and spans 23.5 kb of genomic DNA. The 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 situ hybridization analysis localized the HKα2 gene to murine chromosome 14C3. Sequence analysis of 7.2 kb of the 5′-flanking region revealed numerous consensus sites for transcription factors, including two potential glucocorticoid response elements. Transient transfection of promoter-luciferase constructs demonstrated strong basal HKα2 promoter activity in renal collecting duct cells but not in fibroblasts or in a medullary thick ascending limb of Henle’s loop cell line. Deletion analysis revealed that the proximal 0.2 kb of the promoter was sufficient to confer activity in collecting duct cells. These data should prove important in elucidation of the mechanisms controlling the differential, tissue-specific expression of the HKα2 gene.