Identification of multiple regulatory elements of human L-histidine decarboxylase gene

Previously, we reported the structure of human L-histidine decarboxylase gene. To identify the regions that regulate the tissue-specific expression of HDC, we constructed a fusion DNA with the 5'-flanking region from -1003 to +99 of the HDC gene and chloramphenicol acetyltransferase (CAT) gene, which was then transfected into human basophilic leukemia KU-812-F cells or human epithelial carcinoma HeLa cells. The 1102 bp DNA fragment stimulated the CAT activity in KU-812-F cells, but not in HeLa cells. CAT analysis with a series of 5'-deletion constructs of the HDC-CAT gene revealed the existence of two positive and one negative regulatory elements at -855 to -841 and -532 to -497 and -829 to -821, respectively. Sequence analysis showed a nuclear factor c-Myb binding motif, TAACTG, at position -520. Gel mobility shift analysis showed that the nuclear extract of KU-812-F cells, but not that of HeLa cells, contains a factor which can bind to this motif. These results suggest that the 5'-flanking region of the HDC gene contains multiple regulatory elements for HDC gene expression and that at least one element, including a c-Myb binding motif, is responsible for the tissue-specific expression of HDC.