Human Placental Na+,K+-ATPase α Subunit: cDNA Cloning, Tissue Expression, DNA Polymorphism, and Chromosomal Localization

A 2.2-kilobase clone comprising a major portion of the coding sequence of the Na+,K+-ATPase α subunit was cloned from human placenta and its sequence was identical to that encoding the α subunit of human kidney and HeLa cells. Transfer blot analysis of the mRNA products of the Na+,K+-ATPase gene from various human tissues and cell lines revealed only one band (≈ 4.7 kilobases) under low and high stringency washing conditions. The levels of expression in the tissues were intestine > placenta > liver > pancreas, and in the cell lines the levels were human erythroleukemia > butyrate-induced colon > colon > brain > HeLa cells. mRNA was undetectable in reticulocytes, consistent with our failure to detect positive clones in a size-selected (>2 kilobases) λ gt11 reticulocyte cDNA library. DNA analysis revealed a polymorphic EcoRI band and chromosome localization by flow sorting and in situ hybridization showed that the α subunit is on the short arm (band p11-p13) of chromosome 1.