FUNCTION OF THE RETINOBLASTOMA PROTEIN

视网膜母细胞瘤基因是一类癌症基因的原型。 被称为肿瘤抑制基因。肿瘤抑制基因的定义是 两个关键特征：(1)这些基因的突变促进 肿瘤发生学(2)这些基因突变带来的选择优势 基因的丧失是由于基因功能的丧失。我们正在调查 视网膜母细胞瘤基因产物(PRB)的功能。最好理解的人 PRb的功能是作为转录因子的调节因子。在.期间 在上一个赠款周期中，我们描述了PRB和相关的能力 调节E2F转录因子的蛋白质并控制 表达E2F-靶基因。E2F的激活促进细胞周期 在正常细胞中，pRb起抑制E2F依赖的作用 抄写。 人们对形成的蛋白质复合体的生物化学了解很多。 E2F和PRB家族蛋白之间的关系，但这一家族蛋白的体内功能 人们对监管体系知之甚少。在过去两年里，我们有 建立了两个实验系统来检查这些功能 蛋白质。首先，利用同源重组，我们产生了突变体 E2F-1基因在小鼠体内的等位基因及其消除效果的研究 E2F-1功能。先前的研究表明，E2F-1的行为类似于 癌基因在组织培养中过度表达。然而，小鼠缺乏 E2F-1发生了广泛的肿瘤，揭示了E2F-1的作用 抑制体内肿瘤的形成。在下一个赠款周期中，我们建议 继续E2F功能的研究。我们将专注于 E2F-1缺失细胞表型的鉴定 缺乏DP-1(E2F-1的异二聚体伙伴)的细胞表型， 以及缺乏多个pRb调节的E2F S的细胞的表型。 测试pRb/E2F-1复合体在pRb和E2F-1功能中的作用 携带E2F-1特定突变等位基因的小鼠品系的特征 从而消除了这种相互作用。 我们在上一次拨款中启动的第二个功能研究领域 Cycle也给出了意想不到的发现。公共关系科是一个家庭的一员 的蛋白质，包括p107和p130，它们具有很强的结构 同源。在对3T3细胞系进行鉴定的过程中 PRb、p107或p30不合子小鼠胚胎，我们观察到pRb、p107和p30不合子的小鼠胚胎 P107或p130对脂肪细胞具有特异性和相反的作用。 差异化。而pRb促进分化，p107和p130 阻断脂肪细胞分化。我们已经完成了初赛 对这些差异的描述，以及在下一轮 格兰特将调查PRB p107和PRB p107的功能差异 P130在脂肪形成和其他已定义的分化系统中的作用。

The retinoblastoma gene is the prototype of a class of cancer genes known as tumor suppressor genes. Tumor suppressor genes are defined by two key characteristics: (1) mutation of these genes promotes tumorigenesis (2) the selective advantage conferred by mutation of these genes is due to the loss of gene function. We are investigating the function of the retinoblastoma gene product (pRB). The best understood function of pRB is as a regulator of transcription factors. During the last grant cycle we characterized the ability of pRB and related proteins to regulate the E2F transcription factor and to control the expression E2F-target genes. The activation of E2F promotes cell cycle progression and, in normal cells, pRB acts to repress of E2F-dependent transcription. A great deal is known about the biochemistry of protein complexes formed between E2F and pRB-family proteins but the in vivo functions of this regulatory system are poorly understood. In the last two years we have established two experimental systems to examine the functions of these proteins. First, using homologous recombination we generated mutant alleles of E2F-1 in the mouse and studied the effects of eliminating E2F-1 function. Previous work had shown that E2F-1 behaved as an oncogene when over-expressed in tissue culture. However mice lacking E2F-1 developed a broad range of tumors revealing that E2F-1 acts to suppress tumor formation in vivo. In the next grant cycle we propose to continue this investigation of E2F function. We will concentrate on the characterization of the phenotype of E2F-1 null cells, on the phenotype of cells lacking DP-1 (the heterodimeric partner of E2F-1), and on the phenotype of cells lacking multiple pRB-regulated E2F s. To test role of the pRB/E2F-1 complex in pRB and E2F-1 functions we will characterize mouse strains carrying specific mutant alleles of E2F-1 that eliminate this interaction. A second area of functional studies that we initiated in the last grant cycle has also given unexpected findings. pRB is one member of a family of proteins, including p107 and p130, which share strong structual homologies. During the characterization of 3T3 cell lines prepared from pRB, p107 or p30 nullizygous mouse embryos, we observed that pRB, and p107 or p130 have specific and opposite effects on adipocyte differentiation. Whereas pRB promotes differentiation, p107 and p130 block adipocyte differentiation. We have finished the initial characterization of these differences and in the next round of this grant will investigate the functional differences between pRB p107 and p130 in adipogenesis and in other defined differentiation systems.