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 t he rat CDO gene were isolated and characterized. The CDO gene spanned about 15 kb, and comprised 5 exons. All boundaries between the exons a nd 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 re gion contained a TATA-box-like sequence and putative cis-acting regula tory elements. The 3' end of CDO was polyadenylated at several sites. Northern blots of RNA from rat tissues revealed the highest CDO mRNA l evel in the liver. Significant levels were observed in the kidney, lun g and brain, implying tissue-specific differences in CDO promoter func tion.