Housekeeping Na,K-ATPase α1 Subunit Gene Promoter Is Composed of Multiple cis Elements to Which Common and Cell Type-Specific Factors Bind

Abstract

Na,K-ATPase α1 subunit gene (ATP1A1) is one of the housekeeping genes involved in homeostasis of Na⁺ and K⁺ in all animal cells. We identified and characterized the cis-acting elements that regulate the expression of ATP1A1. The region between −155 and −49 was determined as a positive regulatory region in five cultured cell lines of different tissue origins (MDCK, B103, L6, 3Y1, and HepG2). The region was divided into three subregions: from −120 to −106 (including the Sp1 binding site), from −102 to −61, and from −58 to −49 (including an Sp1 consensus sequence). Cell type-specific factors binding to the middle subregion (from −102 to −61) were detected by gel retardation analysis, using nuclear extracts prepared from MDCK and B103 cells. Two gel retardation complexes were formed in the B103 nuclear extract, and three were formed in the MDCK nuclear extract. DNA binding regions of these factors were located at −88 to −69 and differed from each other in DNase I footprinting experiments. These factors also showed different binding characteristics in gel retardation competition and methylation interference experiments. The identified cis element was named the ATP1A1 regulatory element. The core sequence of this element is found in several other genes involved in cellular energy metabolism, suggesting that the sequence is a common regulatory element responsive to the state of energy metabolism.