Inflammation and ischemia - reperfusion tissue injury are important pa
thophysiologic processes with a wide spectrum of clinical presentation
s; the enzyme xanthine dehydrogenase/oxidase (XDH/XO) is thought to pl
ay a key role in ischemia-reperfusion injury. Recent studies have show
n the transcriptional regulation of XDH/XO by cytokines (Dupont et al.
, 1992, J. Clin. Invest. 89, 197 - 202). In the present study, the 5'
structure of the XDH/XO gene and characterization of its promoter are
undertaken providing an initial step to further elucidate the regulato
ry mechanism(s) of this enzyme. XDH/XO cDNA from rat bone marrow macro
phage has been isolated and used to screen a rat genomic library in or
der to identify and characterize the promoter of the XDH/XO gene. By S
outhern analysis, XDH/XO was found to be a single copy gene in the rat
genome. Primer extension, RNase protection, and anchor-PCR studies in
dicate the presence of multiple start sites within a 65 bp window loca
ted some 20 - 85 bp upstream of the translation initiator (ATG). Funct
ional studies of the sequences up to 116 nt upstream of the translatio
nal start site, which encompasses the several transcriptional start si
tes, indicate that this region is sufficient to drive the expression o
f a luciferase reporter gene and is presumed to represent the promoter
. Neither a TATA box nor a CC-rich region are present in close proximi
ty to any of the transcriptional start sites; however, sequences with
homology to known initiator elements are found within this 116 bp frag
ment. Several possible regulatory elements, including a NF-IL6 motif,
are also located upstream of the transcriptional start site. This stud
y represents the first description of the XDH/XO promoter from a verte
brate system.