Higashi Y, Tanae A, Inoue H, Hiromasa T, Fujii-Kuriyama Y
Department of Biochemistry, Cancer Institute, Tokyo, Japan.
Proc Natl Acad Sci U S A. 1988 Oct;85(20):7486-90. doi: 10.1073/pnas.85.20.7486.
Four steroid 21-hydroxylase B [P-450(C21)B] genes (designated P.7, P.10-1, P.10-2, and P.3) from three P-450(C21)-deficient patients were isolated to analyze their structures and functions. Several base changes were observed in the sequences of the four P-450(C21)B genes as compared to that of the functional B gene. Many of these base changes were identical to those of the P-450(C21)A pseudogene. The three DNAs (P.10-1, P.10-2, and P.3) produced no P-450(C21) activity in a functional assay for P-450(C21) by the COS cell expression system, while the P.7 DNA expressed the activity. The P.10-1 and P.10-2 DNAs were shown to have a point mutation in the second intron, causing aberrant splicing. The P.3 DNA carried three clustered missense mutations in the sixth exon, which impaired P-450(C21) activity. All these critical mutations could be seen in the corresponding site of the P-450(C21)A pseudogene. These data strongly suggest the involvement of gene conversion in this genetic disease.
从三名细胞色素P-450（C21）缺乏症患者中分离出四个类固醇21-羟化酶B [P-450（C21）B]基因（分别命名为P.7、P.10-1、P.10-2和P.3），以分析其结构和功能。与功能性B基因序列相比，在这四个P-450（C21）B基因序列中观察到了几个碱基变化。其中许多碱基变化与P-450（C21）A假基因的碱基变化相同。在COS细胞表达系统对P-450（C21）的功能测定中，这三个DNA（P.10-1、P.10-2和P.3）未产生P-450（C21）活性，而P.7 DNA表达了该活性。已证明P.10-1和P.10-2 DNA在第二个内含子中有一个点突变，导致异常剪接。P.3 DNA在第六个外显子中携带三个成簇的错义突变，损害了P-450（C21）活性。所有这些关键突变都可以在P-450（C21）A假基因的相应位点看到。这些数据强烈表明基因转换参与了这种遗传疾病。
