The CYP2C23 gene is expressed constitutively in the rat liver and kidn
ey, It exhibits different profiles of expression in the two tissues, s
uggesting that several regulation processes could exist, In this paper
, we report the structure of the 5'-flanking region of the CYP2C23 gen
e; 4.5 kbp were sequenced and analyzed, The CYP2C23 gene is present as
a single copy into the rat genome and an unique transcription start s
ite is used in both liver and kidney, Four DNase I hypersensitive site
s have been mapped to the distal part of the hepatic promoter and thre
e are detected in the kidney: only one site is present in the two tiss
ues (L3/K1), In the proximal region, one site is specific for the kidn
ey and one is detected in all the tissues tested, Footprint experiment
s allowed precise identification of the sequence of protected regions:
HNF4 and CREB binding moths are present in the distal liver-specific
sites, moths for AP-1, NF-1, and XRE-Bf are in the distal kidney site,
and a Tf-LF1 binding site is localized in the L3/K1 protected site, I
n the proximal region, a sequence protected in all tissues contains a
SP1/NF kappa B moth whereas a sequence containing a HNF-4 binding moth
is exclusively protected by kidney nuclear extracts, Altogether, the
data clearly demonstrate that trans-acting factors involved in CYP2C23
gene expression differ in liver and kidney.