Structure and function of promotor region of L-histidine decarboxylase gene

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L-histidine decarboxylase (HDC) is a unique enzyme to catalize histamine formation in mamals. This enzyme is expressed in basophils/mast cells and the regulation of its gene expression is important for allergic reaction. To investigate the regulation of HDC gene expression, we cloned HDC genomic DNA and determined its whole structure which consists of 12 exons encompassing 24 kbp. Southern blot analysis indicated that HDC gene is a single gene. In addition, primer extension analysis elucidate that transcriptional initiation site is 92 upper stream of 5' side from first exon. In this consequense, the whole research project in 1993 was carried out and these results were reported in J.Biol.Chem.265 : 1554-1559,1994. Furthermore, we determined more than 2000bp nucleic acid sequenses of the 5' side of HDC and found TATA like sequense, GC box, CACC box, GATA consensus sequence, LBP-1 binding sequence in promotor area. GATA transcriptional factors are involved in differentiation of hematopoietic cells and especially, GATA-1 and GATA-2 are thought to play an important role in the differentiation of basophils and mast cells. In fact, high binding activity to GATA-2 probe was found in the nuclear extract from KU-812F and HMC-1 with gel shift assay.This result suggested that GATA-2 is involved in the induction of HDC gene expression as well as in the differentiation of basophils and mast cells. To prove this, we performed deletion asay with reporter gene. However, we have not the evidence to indicate that GATA binding site is functioning to induce HDC gene expression. To date, we found that suppressive element exists between -273 and -153 nucleic acid sequense in 5' upper stream of first exon of HDC gene and need to study more.