人類

人類 CYP21B 基因之 -104 位置與核蛋白的結合影響該基因之基本

轉錄活 性

-104G residue of the human CYP21B gene is important for the basal transcriptional activity and the nuclear protein interaction

中文摘要

P450c21 氫氧化酵素發生缺失會導致一種隱性的遺傳疾病，腎上腺皮質增 生症。人類的 P450c21 氫氧化酵素基因有兩套，一是可以轉譯產生活性 酵素的 CYP21B 基因，另一個則是假基因，CYP21A。我們實驗室之前的實 驗結果顯示，該基因的 -167/-64 區域決定 CYP21 基因基本轉錄活性的表 現，而且 CYP21B 基因該區域與核蛋白間之結合較 CYP21A 的同區域基因 強，因而推測這可能是導致二基因啟動子表現活性差異的原因。同時，比 較 CYP21A 與 CYP21B 在此區域內的基因序列，可發現只有四個位置的不 同。本篇論文主要是研究這些核甘酸序列是否均對該基因與核蛋白間之結 合力具有其重要性。實驗結果顯示，若將 CYP21B 上 -104 位置的 G 改 成 CYP21A 序列的 A 時，則會明顯下降其與核蛋白的結合力，這表示 -104 位置的核甘酸序列對於 CYP21B 基因與核蛋白作用上有決定性的影 響。另外也發現，若將這 -104 位置的核甘酸序列改變時，則會使得 CYP21B 基因的基本轉錄活性表現下降約 60%。此外，亦發現在腎上腺皮 質細胞中有多種的核蛋白可與 CYP21B 的 -123/-88 DNA 區域相結合。若 使用帶有突變序列之相同 DNA 區域作為探針時，亦觀察到可與 21B 結合 相似的核蛋白質存在於所測試的各種細胞核萃取物中。因此綜合我們的實 驗結果，顯示 -104 位置之基因序列的改變，會經由改變 CYP21B 與核蛋 白質的結合力，而影響該基因之基本轉錄活性。

英文摘要

Enzymatic deficiency of 21-hydroxylase causes the congenital adrenal hyperplasia (CAH), an autosomal recessive disorder.

There are two copies of human P450c21-hydroxylase gene, the active CYP21B gene which encodes the active enzyme, and the

pseudogene, CYP21A. It's known that the -167/-64 region of CTP21 gene determined its basal transcription activity. Based on its

higher transcription activity and nuclear protein binding

affinity of CYP21B gene, the authors therefore hypothesized that differences on the promoter strength of CYP21A and CYP21B genes may be due to their different protein binding affinity.

Comparing the sequences within that region of the CYP21A and CYP21B genes, there are only four nucleotides differences. In this study, we analyzed the role of individual gene-specific nucleotides within that region for the transcription activity and protein binding ability. Our results showed that both protein binding ability and transcription activity of CYP21B gene were decreased when G residue at -104 position changed to the CYP21A sequence, A. We also found that multiple nuclear proteins present in adrenal cells could interact with the

-123/-88 region of CYP21 gene, but -104G→A did not affect the species of proteins which could bind to the -123/-88 region of CYP21 gene. In summary, our results indicated that the G residue at -104 position of the CYP21B gene is important for both of the DNA-protein interaction and basal transcription activity of CYP21B gene.