Molecular cloning and characterization of the human xanthine dehydrogenase gene (XDH)

Xanthine dehydrogenase (XDH, EC 1.1.1.204) is a rate-limiting enzyme in the oxidative metabolism of purines and is thought to play a key role in a variety of pathophysiologic processes including ischemiasolidusreperfusion injury, viral pneumonia, and renal failure. We herein report the isolation and characterization of the human XDH gene. The gene is composed of 36 exons and 35 introns and spans at least 60 kb. The exon sizes range from 53 to 279 bp, and the intron sizes range from 0.2 to over 8 kb. Using primer extension and RNase protection analyses, two transcriptional initiation sites were identified 59 and 82 nucleotides upstream of the ATG start codon. One Goldberg-Hogness box (ATTTAT)-like sequence was found 24 bp upstream from the second transcriptional initiation site, and two inverted CCAAT sequences were found 19 and 42 bp upstream from the second transcriptional initiation sites. A relative GC-enriched region was found between -55 and -121. Approximately 2 kb of the 5'-flanking region was sequenced, and a variety of putative regulatory elements were identified including CsolidusEBP binding sites, IL-6 and NF-kappaB sites, and potential TNF-RE, IFN-gamma-RE, and IL-1-RE sites.