The rat H⁺/K⁺-ATPase β subunit gene and recognition of its control region by gastric DNA binding protein

The rat gastric H⁺/K⁺-ATPase β subunit gene was cloned, and its nucleotide sequence was determined. The coding region is separated by 6 introns, whereas the related human Na⁺/K⁺-ATPase β subunit gene was shown to have 5 introns (Lane, L. K., Shull, M. M., Whitmer, K. R., and Lingrel, J. B. (1989) Genomics 5, 445-453). The positions of introns 1, 2, and 5 of the two genes were the same. The similarities in intron/exon organizations and primary structures (30-40% identical residues) suggest that the β subunit genes for H⁺/K⁺- and Na⁺/K⁺-ATPases were derived from a common ancestor. The upstream region of the rat H⁺/K⁺-ATPase β subunit gene contains direct repeat sequences and palindromes, potential binding sites for RNA polymerase II and E4TF1, and CACCC box sequences. Gel retardation assay demonstrated that the stomach, but not other tissues (liver, brain, kidney, spleen, and lung), has a nuclear protein(s) capable of binding to the regions upstream of the potential RNA polymerase II binding sites (TATA box). The nuclear protein(s) are suggested to recognize three tandem GA-TAGC sequences and may be important for controlled transcription of the H⁺/K⁺-ATPase β subunit gene in gastric parietal cells.