It is important to know the regulation of the expression of the mac25 gene
because of its reduced expression in several cancer cells and of its induct
ion by some hormonal factors. We cloned the promoter region of the murine m
ac25 gene and found five repeats of CCAAT sequences, four Sp1 sites, a TATA
-like sequence, and an initiator (INR) sequence. Analysis using luciferase
reporter plasmids indicated that CCAAT repeats have a strong enhancer activ
ity and the second to fourth Sp1 sites are essential for basal activity of
the expression of the mac25 gene. The 1 kb region that contains the promote
r and exon 1 of the mac25 gene was in a typical CpG island. As hypermethyla
tion and reduced expression of the mac25 gene were reported in murine liver
tumors, methylation of this CpG island may be directly associated with the
expression of the mac25 gene and tumorigenesis. (C) 2000 Academic Press.