Boehmelt G, Ulrich E, Kurzbauer R, Mellitzer G, Bird A, Zenke M
Institute of Molecular Pathology, Vienna, Austria.
Cell Growth Differ. 1994 Feb;5(2):221-30.
The molecular cloning and initial characterization of the complementary DNA encoding the chicken homologue of the human retinoblastoma susceptibility gene product Rb are described. Chicken Rb (chRb) was found to be highly homologous to human, mouse, and Xenopus Rb in primary amino acid sequence, underlining its conserved function in cell cycle control in higher eukaryotes. The highest level of homology was found within the Rb "pocket domains" and at the Rb COOH terminus, whereas the extreme NH2 terminus of chRb is divergent. We also show that transcription of chRb initiates at multiple start sites within a DNA segment which represents a CpG island. ChRb is transcribed as a 4.7-kilobase (kb) mRNA species in a variety of normal chicken tissues and oncogene-transformed hematopoietic cells. However, in v-rel-transformed cell lines, a variant 3.1-kb Rb-specific mRNA was detected in addition to the 4.7-kb transcript. ChRb is expressed as a 104 kilodalton protein and is therefore slightly smaller than the mammalian Rb proteins.
本文描述了编码人类视网膜母细胞瘤易感基因产物Rb的鸡同源物的互补DNA的分子克隆及初步特征分析。发现鸡Rb（chRb）在一级氨基酸序列上与人类、小鼠和非洲爪蟾的Rb高度同源，这突出了其在高等真核生物细胞周期调控中的保守功能。在Rb“口袋结构域”内和Rb的COOH末端发现了最高水平的同源性，而chRb的极端NH2末端则有所不同。我们还表明，chRb的转录起始于代表一个CpG岛的DNA片段内的多个起始位点。在多种正常鸡组织和癌基因转化的造血细胞中，chRb转录为一种4.7千碱基（kb）的mRNA。然而，在v-rel转化的细胞系中，除了4.7-kb转录本外，还检测到一种3.1-kb的Rb特异性变异mRNA。chRb表达为一种104千道尔顿的蛋白质，因此略小于哺乳动物的Rb蛋白。
