Promoter structure of human sonic hedgehog gene

Sonic hedgehog (Shh) is a secreted signal transducer responsible not only f or patterning of the anterior-posterior axis during early limb and neuronal development, but also for generating cell-type diversity at later developm ental stages. To elucidate the mechanism regulating human Shh gene expressi on, we cloned the 5'-flanking region of the human Shh gene and characterize d it by transient transfection studies. Two transcription start sites were identified by primer extension analysis. Two TATA-boxes, a CCAAT-box and a palindrome-like structure constituted the basic promoter structure. Further more, two continuous E-boxes and a putative homeodomain containing an ATTA- box were located around 350-450 bp upstream of the upper TATA-box. Consensu s binding sites of the RA, estrogen, D3 and glucocorticoid/progesterone rec eptors were not found within the cloned sequence. Short-term treatment with TPA increased luciferase activity up to 2.1-fold; on the other hand, treat ment with dibutyryl-cyclic AMP decreased it to 0.8-fold. Retinoic acid (RA) , vitamin D3, dexamethazone (DEX) and estradiol (E2) had no effect on the l uciferase activity. Since the zebrafish Shh promoter contains two closely s paced axial (HNF3 beta) binding sequences on its basic promoter, the palind rome-like structure located in the corresponding site of the human Shh prom oter may be a crucial binding domain regulating human Shh gene expression. (C) 1998 Elsevier Science B.V. All rights reserved.