Activation of the Na+/H+ exchanger gene by the transcription factor AP-2.
We have isolated and characterized regions important for expression of the mouse Na+/H+ exchanger gene. A 1.1-kilobase fragment upstream of the 5'-untranslated region contains specific DNA motifs characteristic of promoter and enhancer elements including a TATA box, two CAAT boxes, an SP-1 site, a cyclic AMP response element-binding site, and an AP-2-like site. This 1.1-kilobase fragment directs transcription of a luciferase reporter gene in mouse fibroblasts (NIH 3T3) and human Hep G2 cells. Deletion or mutation of an AP-2-like site 100 base pairs from the start site of transcription resulted in loss of most of the reporter plasmid activity. In addition, cotransfection of an AP-2 expression plasmid and the mouse promoter/luciferase plasmid increased the amount of Na+/H+ exchanger-directed transcription in AP-2-deficient Hep G2 cells. Moreover, mobility shift analysis indicated that a putative AP-2-binding site is capable of binding purified AP-2 protein and a specific protein from nuclear extracts of NIH 3T3 cells. The results show that the transcription factor AP-2 may play an important role in regulation of transcription of the mouse Na+/H+ exchanger gene.
Department of Pediatrics, Faculty of Medicine, University of Alberta, Edmonton, Canada.
J R
JR
Dyck
N L
NL
Silva
L
L
Fliegel
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011817:Rabbits; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics*; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D017923:Sodium-Hydrogen Exchangers; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D004247:DNA