Coding defect and a TATA box mutation at the bilirubin UDP-glucuronosyltransferase gene cause Crigler-Najjar type I disease
Coding defect and a TATA box mutation at the bilirubin UDP-glucuronosyltransferase gene cause Crigler-Najjar type I disease
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DOI：
10.1016/s0925-4439(98)00030-1
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发表时间：
1998-07-01
影响因子：
6.2
通讯作者：
Owens, IS
中科院分区：
文献类型：
--
作者：
Ciotti, M;Chen, F;Owens, IS
在胆红素尿苷二磷酸葡萄糖醛酸转移酶（转移酶）基因的突变在严重高胆红素血症Crigler-Najjar（CN）I型个人与中度高胆红素血症CN II个人进行了比较。本研究中的CN-I（CF）患者持续存在TATA盒插入突变，该突变与第二等位基因的编码缺陷配对，与之前在CN-I患者中观察到的所有编码缺陷不同。突变TATA盒[A（TA）（8）A]（也见于CN-II患者）的序列与野生型盒[A（TA）IA]的序列进行比较。当存在于胆红素转移酶UGT 1A 1基因的~ 1.7kb上游调控区（URR）时，[A（TA）（8）A]的转录活性是野生型盒的10-15%，所述胆红素转移酶UGT 1A 1基因与氯霉素乙酰转移酶报告基因pCAT 1.7H融合并转染到HepG 2细胞中。此外，制备具有TA缺失的构建体[A（TA）（6）A]并用作对照;转录活性为65%正常。在CF（CN-1）中观察到的编码区缺陷R336 W位于胆红素转移酶UGT 1A 1 [HUG-Brl] cDNA中，其相应的蛋白质被命名为UGT 1A 1 *32。当在COS-1细胞中表达时，UGT 1A 1 *32蛋白支持0-10%正常胆红素葡萄糖醛酸化。在SM（CN-II）中第二个等位基因处观察到的I294 T编码缺陷产生了UGT 1A 1 *33突变蛋白，其支持40-55%的正常活性，胆红素的K-m（2.5 μ M）正常。与CF不同，SM中观察到的高胆红素血症对苯巴比妥治疗有反应。患者的父母是后代中发现的相应突变的携带者。因此，与有害错义突变配对的TATA盒突变在CN-1患者中是完全抑制性的，并且是致死基因型/表型的原因;但是当纯合时，即与自身配对时，如先前在文献中报道的，其抑制性低得多，并且产生轻度吉尔伯特表型。(C)1998 Elsevier Science B. V.保留所有权利。
Mutations at the bilirubin UDP-glucuronosyltransferase (transferase) gene in a severely hyperbilirubinemic Crigler-Najjar (CN) type I individual was compared with that in a moderately hyperbilirubinemic CN II individual. The CN-I (CF) patient in this study sustained a TATA box insertional mutation which was paired with a coding defect at the second allele, unlike all coding defects previously seen in CN-I patients. The sequence of the mutant TATA box, [A(TA)(8)A], also seen in the CN-II patient, was compared with that at the wild-type box, [A(TA) IA]. Transcriptional activity with [A(TA)(8)A] was 10-15% that with the wild-type box when present in the -1.7 kb upstream regulatory region (URR) of the bilirubin transferase UGT1A1 gene which was fused to the chloramphenicol acetyl transferase reporter gene, pCAT 1.7H, and transfected into HepG2 cells. Also, a construct with a TA deletion, [A(TA)(6)A], was prepared and used as a control; transcriptional activity was 65% normal. The coding region defect, R336W, seen in CF (CN-I) was placed in the bilirubin transferase UGT1A1 [HUG-Brl] cDNA, and its corresponding protein was designated UGT1A1*32. The UGT1A1*32 protein supported 0-10% normal bilirubin glucuronidation when expressed in COS-1 cells. The I294T coding defect seen at the second allele in SM (CN-II) generated the UGT1A1*33 mutant protein which supported 40-55% normal activity with a normal K-m (2.5 mu M) for bilirubin. The hyperbilirubinemia seen in SM decreased in response to phenobarbital treatment, unlike that seen in CF. Parents of the patients were carriers of the respective mutations uncovered in the offspring. The TATA box mutation paired with a deleterious missense mutation is, therefore, completely repressive in the CN-I patient, and is responsible for a lethal genotype/phenotype; but when homozygous, i.e. paired with itself, as previously reported in the literature, it is far less repressive and generates the mild Gilbert's phenotype. (C) 1998 Elsevier Science B.V. All rights reserved.