STRUCTURAL ORGANIZATION AND CHROMOSOMAL LOCALIZATION OF THE HUMAN NA,K-ATPASE BETA-3 SUBUNIT GENE AND PSEUDOGENE

We have clone and characterized the Na,K-ATPase beta 3 subunit gene (A TPIB-3), and a b3 subunit pseudogene (ATP IB3P1), from a human PAC gen omic library. The beta 3 subunit gene is > 50 kb in size and is split into 7 exons. The exon/intron organization oi the beta 3 subunit gene is identical to that of the Na,K-ATPase beta 3 subunit gene, indicatin g that those two genes evolved from a common evolutionary ancestor. Co mparison of the promoter region of the human and mouse beta 3 subunit gene reveals a high degree of homology within a 300-bp segment located immediately upstream of the translation start side, suggesting that c ontrol elements that serve to regulate the cell-specific expression of the beta 3 subunit gene are likely to be located within this conserve d region. Dot blot analysis of beta 3 subunit transcripts revealed exp ression within virtually all human tissues, while in situ hybridizatio n showed expression of beta 3 mRNA in both neurons and glia of rat bra in. Fluorescence in situ hybridization with PAC DNA clones localized A TPIB3 to the q22 -->-23 region of Chromosome(Clr) 3, and the beta 3 ps edogene to the P13 -->-15 region of Chr 2.