STRUCTURE OF THE HUMAN RETINOBLASTOMA GENE
STRUCTURE OF THE HUMAN RETINOBLASTOMA GENE
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DOI：
10.1073/pnas.86.14.5502
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发表时间：
1989-07-01
影响因子：
11.1
通讯作者：
LEE, WH
中科院分区：
文献类型：
--
作者：
HONG, FD;HUANG, HJS;LEE, WH
人类视网膜母细胞瘤基因(RB)的完全失活被认为是几种不同癌症发生的关键步骤。为了提供一个了解失活机制的框架，我们描绘了RB的结构。Rb转录本编码27个外显子，分布在约2000 kb的基因组DNA中。单个外显子的长度从31个碱基对到1889个碱基对。最大的内含子跨度为60kb，最小的内含子只有80bp。外显子13-17的缺失常见于各种类型的肿瘤，包括视网膜母细胞瘤、乳腺癌和骨肉瘤，并预测该区域存在潜在的重组热点。一个假定的“亮氨酸-拉链”基序完全由外显子20编码。这里给出的详细的RB结构应该被证明是有用的，以确定其编码蛋白的潜在功能结构域。Rb的转录是在多个位置启动的，起始位置周围的序列具有很高的G+C含量。一个典型的上游塔塔盒子不存在。利用含有细菌氯霉素乙酰转移酶基因的异源表达系统对Rb启动子区域进行定位。缺失分析表明，Rb启动子的小至70bp的区域就足以产生活性，这与其他已鉴定的富含G+C的基因启动子相似。在启动子区域发现了几个直接重复序列和可能的茎环结构。在所研究的7.3kb的上游序列中没有检测到增强子元件。Rb启动子的几个特征使人联想到与许多“家务”基因相关的特征，这与其普遍存在的表达模式一致。
Complete inactivation of the human retinoblastoma gene (RB) is believed to be an essential step in tumorigenesis of several different cancers. To provide a framework for understanding inactivation mechanisms, the structure of RB was delineated. The RB transcript is encoded in 27 exons dispersed over about 2000 kilobases (kb) of genomic DNA. The length of individual exons ranges from 31 to 1889 base pairs (bp). The largest intron spans > 60 kb and the smallest one has only 80 bp. Deletion of exons 13-17 is frequently observed in various types of tumors, including retinoblastoma, breast cancer, and osteosarcoma, and the presence of a potential "hot spot" for recombination in the region is predicted. A putative "leucine-zipper" motif is exclusively encoded by exon 20. The detailed RB structure presented here should prove useful in defining potential functional domains of its encoded protein. Transcription of RB is initiated at multiple positions and the sequences surrounding the initiation sites have a high G + C content. A typical upstream TATA box is not present. Localization of the RB promoter region was accomplished by utilizing a heterologous expression system containing a bacterial chloramphenicol acetyltransferase gene. Deletion analysis revealed that a region as small as 70 bp is sufficient for RB promoter activity, similar to other previously characterized G + C-rich gene promoters. Several direct repeats and possible stem-and-loop structures are found in the promoter region. No enhancer element was detected within the 7.3 kb of upstream sequence studied. Several features of the RB promoter are reminiscent of the characteristics associated with many "housekeeping" genes, consistent with its ubiquitous expression pattern.