STRUCTURE AND EXPRESSION OF THE MOUSE AHR NUCLEAR TRANSLOCATOR (MARNT) GENE

Aryl hydrocarbon receptor (AhR) nuclear translocator (Amt) gene has be en isolated and characterized from a mouse genomic DNA library. The ge ne is about 60 kilobases long and split into 22 exons, An unusual exon /intron junctional sequence was found in the 11th intron of the gene t hat begins with GC at its 5'-end, The exon/intron arrangement of mArnt gene differs greatly from those of the other members of the same basi c-helix-loop-helix/PAS family. The gene is TATA-less and has several t ranscription start sites. The promoter region of the mArnt gene is GC- rich and contains a number of putative regulatory DNA sequences such a s two GC-boxes, a cAMP-responsive element, E-box, AP-1 site, and CAAT- box. Deletion experiments revealed that all these DNA elements made su bstantial contributions to a high level of expression of the gene, exc ept for the cAMP-responsive element. Of all, two GC-boxes displayed th e most dominant enhancing effects. It was demonstrated that there exis t specific factors binding to these DNA elements in the nuclear extrac ts of HeLa cells. Among them, Sp1 and Sp3, and CAAT-box binding factor -A were identified to bind the GC-boxes and CAAT-box, respectively. Ex pression of MyoD in HeLa cells stimulated the Amt promoter activity by binding to the E-box.