Wei Kuo Chen, Berger Mitchel S, Sehgal Anil
Chang Gung Memorial Hospital, 1st Division of Neurosurgery, Taoyuan, Taiwan.
Anticancer Res. 2002 Mar-Apr;22(2A):745-53.
Using the technique of differential hybridization of a human fetal brain library, we identified a novel gene, brain 1 (BR-1). This gene is expressed in normal brain but has low or no expression in human gliomas. We have cloned and sequenced the full-length cDNA corresponding to this gene. A data base search for the nucleotide sequence homology was performed for BR-1. The BR-1 sequence showed strong homology to a human genomic clone from chromosome 2. Moderate sequence homology was observed between BR-1 and an expressed sequence tag (EST) from a human placenta library. Three different regions of BR-1 also showed homology to a mouse EST that is similar to EL-10 gene. Sequence analysis indicated that the protein sequence for BR-1 has one tyrosine kinase phosphorylation site and two N-myristoylation sites. Northern blot analysis indicated that the BR-1 gene is expressed in heart, placenta, lung, liver, skeletal muscle, kidney and pancreas. A low level of expression of BR-1 is observed in the cerebellum, cerebral cortex, spinal cord, occipital lobe and putamen. The BR-1 gene is also expressed in fetal brain, liver and kidney. Low expression of BR-1 gene was observed in a number of non-brain tumor cell lines. RT-PCR analysis indicated that the BR-1 gene was expressed in non-neoplastic (epilepsy specimens) but not in six oligodendrogliomas and three oligoastrocytoma tumor samples analyzed. BR-1 was not expressed in either seven low grade gliomas or eight grade IV glioblastoma tumor tissue samples analyzed. Three glioblastoma cell lines did show low expression of the BR-1 gene. On the basis of its expression properties, we conclude that BR-1 is a potential novel tumor suppressor gene.
利用人胎儿脑文库的差异杂交技术，我们鉴定出一个新基因——脑1（BR-1）。该基因在正常脑中表达，但在人类胶质瘤中表达低或无表达。我们已经克隆并测序了与该基因对应的全长cDNA。对BR-1进行了核苷酸序列同源性的数据库搜索。BR-1序列与来自2号染色体的人类基因组克隆显示出很强的同源性。在BR-1与来自人胎盘文库的一个表达序列标签（EST）之间观察到中等程度的序列同源性。BR-1的三个不同区域也与一个类似于EL-10基因的小鼠EST显示出同源性。序列分析表明，BR-1的蛋白质序列有一个酪氨酸激酶磷酸化位点和两个N-肉豆蔻酰化位点。Northern印迹分析表明，BR-1基因在心脏、胎盘、肺、肝、骨骼肌、肾和胰腺中表达。在小脑、大脑皮层、脊髓、枕叶和壳核中观察到BR-1的低水平表达。BR-1基因也在胎儿脑、肝和肾中表达。在一些非脑肿瘤细胞系中观察到BR-1基因的低表达。RT-PCR分析表明，BR-1基因在非肿瘤性（癫痫标本）中表达，但在所分析的6个少突胶质细胞瘤和3个少突星形细胞瘤肿瘤样本中不表达。在所分析的7个低级别胶质瘤或8个IV级胶质母细胞瘤肿瘤组织样本中，BR-1均未表达。三个胶质母细胞瘤细胞系确实显示出BR-1基因的低表达。基于其表达特性，我们得出结论，BR-1是一个潜在的新型肿瘤抑制基因。
