| Summary: | 碩士 === 台北醫學院 === 細胞及分子生物研究所 === 86 === Steroid 21 hydroxylase (P450c21) is specifically expressed in the adrenal cort
ex, and is required for the biosynthesis of steroid hormones. Enzymatic defici
ency of 21-hydroxylase causes the congenital adrenal hyperplasia (CAH), an aut
osomal recessive disorder. There are two copies of human steroid 21-hydroxylas
e gene, the active CYP21 which encodes the enzyme, and the pseudogene, CYP21P.
These two genes are localized on human chromosome 6p21.1, and duplicated in t
andem with the genes for the fourth components of complement, C4A and C4B, and
other newly characterized duplicated genes, organized as following: 5''C4A(ZA(
CYP21P(YA(XA(C4B(ZB(CYP21(YB(XB-S3''. In this complex locus, most of the transc
ripts are adrenal-specific, including the CYP21, XA, YA, ZA,. XB-S, YB, ZB.To
study the cis-elements controlling the adrenal-specific expression of these ge
nes, we analyzed the effects of DNA sequences upstream from the CYP21P and CYP
21 on the transcription activity of the basic promoter of the CYP21. We used m
ouse adrenocorticoid tumor Y-1 cell, testicular Leydig MA10 cell, and human li
ver Hep G-2 tumor cells to analyze the adrenal-specific expression. After tran
sient transfection into cells, the transcription activity was analyzed using C
AT and primer extension assays. The results showed that DNA sequences at the -
6328/-1668 bp region upstream from the CYP21 enhanced the transcriptional acti
vity of CYP21 to 2 fold in Y-1 cell, but not in MA10 or Hep G-2 cells. However
, smaller DNA fragments covering the same region didn''t show enhanced effect
but suppressed the transcription activity of the CYP21 in all three cell lines
tested. In addition, DNA regions within the 13.5 kb upstream from the CYP21P
all suppressed the transcription activity of the CYP21 but to a different leve
l. Therefore, we predict the regulatory element(s) controlling the adrenal-spe
cific expression of the CYP21 may be located within the -6328/-1668 bp region.
Other cis-elements at the C4/CYP21 gene locus which are not tested in this st
udy may also be involved in the regulation of the tissue-specific expression o
f human steroid 21-hydroxylase. Further study will be performed to test this p
ossibili
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