ATF-1CREB HETERODIMER IS INVOLVED IN CONSTITUTIVE EXPRESSION OF THE HOUSEKEEPING NA,K-ATPASE ALPHA-1 SUBUNIT GENE

Na,K-ATPase alpha 1 subunit is an essential protein for cell growth an d homeostasis. The gene coding for the protein is expressed in various types of tissues. We previously demonstrated that the transcription r egulatory element of the gene (ARE) is located in the position -102 to -61 from the transcription initiation site. To identify the minimal r egions that are essential for the constitutive expression, the sequenc es of the ARE were analyzed in detail by in vitro transcription assays using nuclear extracts from rat kidney, brain and liver. The analyses of various mutations in the promoter demonstrated that the proximal r egion of the ARE is required for the efficient transcription in every nuclear extract. The factors binding to this region in these nuclear e xtracts exhibited identical mobility in gel retardation assays. The AT F/CRE core motif is indicated to be important for the factor binding a nd for the promoter function in all nuclear extracts. The common bindi ng factor in the nuclear extracts was revealed to be an ATF-1/CREB het erodimer by gel retardation assays using specific antibodies. We concl ude that the ATF-1/CREB heterodimer is involved in the constitutive ex pression of the Na,K-ATPase alpha 1 subunit gene.