Epigenetic regulation is a determinant of the cell line specific expression of the UDP glycosyltransferase 3A1 and 3A1 genes

The UDP glycosyltransferases (UGTs) are a super-family of
enzymes involved in the metabolism of xenobiotics and endogenous
molecules. Variations in UGT expression have been associated
with disease states and inter-individual variation in response
to drug therapy. The UGT3A family was discovered and characterised
by our laboratory. Upon investigating UGT3A expression
in a range of cell lines, we found a large number in which
UGT3A1 was not expressed. To determine if epigenetic mechanisms
are responsible for this lack of expression, cell lines were
treated with the demethylating agent 5-aza-20-deoxycytidine (5-
aza-dC), and the histone deacetylase inhibitor trichostatin A
(TSA), and levels of UGT3A mRNA measured. In three cell lines
(T47D, MCF-7 and ZR75.1), 5-aza-dC induced UGT3A1 expression
from 8.9-fold (ZR75.1, p = 0.024) up to 12.2-fold (T47D,
p = 0.007). TSA alone did not induce UGT3A1 expression, but
in some cases, was synergistic with 5-aza-dC. Neither chemical
had an effect on UGT3A2 expression in these three cell lines. In
MDA-MB-453 cells, only 5-aza-dC with TSA induced UGT3A1
expression (14.5-fold, p = 0.036), while UGT3A2 was induced by
5-aza-dC (27.8-fold, p = 0.002), and 5-aza-dC with TSA (23.9-
fold, p = 0.012). Thus our preliminary data indicates that epigenetic
mechanisms, particularly DNA methylation, are a determinant
of cell line specific expression of UGT3A1 and UGT3A2.
Bisulfite sequence analysis will be performed to identify the methylation
status of predicted promoter CpG islands. This should
provide further novel insights into the epigenetic regulation of
the UGT3A family.