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-Reductase
Type 2 Promoter in the Rat Epididymis
Abstract
Steroid 5
-reductase converts testosterone to the
more potent androgen, dihydrotestosterone. The molecular
mechanisms responsible for maintaining high concentrations
of the 5
-reductase type 2 mRNA in the caput
epididymidis and for regulating its region-specific
expression are unknown. To gain insight into its
transcriptional regulation, the cloning and
characterization of the 5'upstream region of
5
-reductase type 2 were undertaken. Sequential
deletion analysis was done to map the 2243-bp cloned
5'upstream region, and the constructs were transfected
into epididymal PC1 cells and prostatic PC3 cells. In both
cell lines, regulatory elements and the minimal promoter
were mapped to the 485-bp region upstream of the start
codon. Primer extension and 5'RACE identified one
transcriptional start site at 33-bp upstream of the start
codon. Using EMSA, a specific band was observed in the
-68 to -32 bp region in the presence of nuclear extracts.
Supershift and mutational studies confirmed the binding of
Sp1, and to a lesser extent Sp3, to the two potential Sp1
binding sites and the preference of these proteins to one
binding site over the other. Sp1 and Sp3 were both
predominantly immunolocalized to the principal cells of
the epididymis and follow distinct distribution patterns
in this tissue. These results provide a framework crucial
in the further investigation of the transcriptional
regulation of 5
-reductase type 2 in the rat
epididymis.
Key words:
Male Reproductive Tract
Epididymis
Gene regulation
Steroid hormones
Testosterone
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