Structural organization and tissue-specific expression of the gene encoding rat cysteine dioxygenase.

Cysteine dioxygenase (CDO) is a key enzyme involved in the metabolism of L-cysteine. Genomic clones containing the 5'-flanking sequence of the rat CDO gene were isolated and characterized. The CDO gene spanned about 15 kb, and comprised 5 exons. All boundaries between the exons and introns matched the GT/AG rule. The major transcription start point (tsp) was A at 213 bp upstream from the ATG codon. The 5'-flanking region contained a TATA-box-like sequence and putative cis-acting regulatory elements. The 3' end of CDO was polyadenylated at several sites. Northern blots of RNA from rat tissues revealed the highest CDO mRNA level in the liver. Significant levels were observed in the kidney, lung and brain, implying tissue-specific differences in CDO promoter function.