Human cysteine dioxygenase gene: Structural organization, tissue-specific expression and downregulation by phorbol 12-myristate 13-acetate

The organization of the human cysteine dioxygenase (CDO) gene was found to be similar to its rat counterpart, and the location of the introns in the p rotein structure was identical to the rat CDO gene. The major transcription start site, identified by primer extension, was located 260 bp upstream fr om the ATG codon. The sequence of the 5'-immediate upstream region was high ly conserved between the human and rat CDO genes. The putative promoter reg ion contained a TATA-box-like sequence, and many putative cis-acting elemen ts including HNF5, GRE, TRE, CRE, CArG box, ARE, MBS, and NF-kB. A Northern blot analysis revealed that CDO mRNA was strongly expressed in the liver a nd placenta, and weakly in the heart, brain and pancreas. CDO mRNA was also detected in human hepatoblastoma HepG2 cells. The CDO mRNA level in HepG2 cells was decreased after 2 h and reached a minimum 6 h-8 h after a phorbol 12-myristate 13-acetate (PMA) treatment, and then gradually returned to th e basal level.