Cloning and analysis of the 5'-flanking region of rat Na+/K(+)-ATPase alpha 1 subunit gene.

We cloned a 13.3 kilobase (kb) fragment of genomic DNA spanning at least the first two exons of the rat Na+/K(+)-ATPase alpha 1 subunit gene (NKAA1) and 1.5 kb of the 5'-flanking region. S1 nuclease mapping analysis of the 5' end of the Na+/K(+)-ATPase mRNA indicated that the transcription initiation site was located 262 base pairs (bp) upstream of the translation initiation codon. The transcription initiation site of the Na+/K(+)-ATPase alpha 1 subunit gene was identical among six tissues of adult rat (kidney, brain, heart, thyroid, liver and lung). A TATA-box-like sequence (at position -32), two Sp1 factor binding sequences (-137, -56), an active transcription factor consensus binding sequence (-71) and two glucocorticoid-responsive element half consensus sequences (-750, -481) were found in the 5'-flanking region. The sequence of the first exon and the 5'-flanking region of the rat NKAA1 was 63% homologous to that of the horse equivalent. Maximum homology (82%) between the two genes was observed in the region from 361 bp upstream of the translation initiation site to the 3' end of the first exon. The TATA-like box, Sp1 binding site and the active transcriptional factor (ATF) consensus site in this region were conserved in both rat and horse.