MESSENGER RNA DECAY OF IMMEDIATE EARLY GENES

在哺乳动物细胞中，c-fos原癌基因是一类典型的 约50-100个生长因子诱导基因，称为即刻 早期基因，其转录产物在细胞质中迅速腐烂 半衰期不到30分钟。这类信使核糖核酸的不稳定性 它与大多数哺乳动物的信息不同，后者通常 更稳定，半衰期从几小时到几天不等。这项建议 重点阐明哺乳动物中即刻早期基因的mRNA降解 细胞，以c-fos原癌基因为模型系统。 文中提出了四个重要问题。首先，在功能上是什么 MRNA不稳定的两个主要c-fos决定因素的重要特征？ 第二，c-fos编码区决定因素的性质是什么？ 不稳定？它的不稳定功能如何与蛋白质偶联 翻译？第三，与c-蛋白相互作用的细胞质因子是什么 FOS不稳定的决定因素？第四，是什么机制使c- FOS mRNA的靶向快速和选择性降解也是原因之一 其他直接早期基因mRNAs的衰变？考试的结果 C-fos基因顺式作用决定簇的结构特征及性质 C-fos编码区的不稳定性决定因素将涉及到 人c-fos和兔β-珠蛋白的明确突变和融合 体外基因，将这些改变的基因结构引入小鼠 成纤维细胞，并分析产生的mRNAs在体内的衰变。这个 细胞质mRNA降解因子的鉴定与鉴定 将涉及在体外系统中重建mRNA衰变和 进行体外信使核糖核酸结合实验。最后，三种基因的mRNA衰变 将对即刻早期基因的mRNAs进行研究，以测试其泛化能力 C-fos信使核糖核酸的衰退机制。 这些研究的结果应该会增强我们对一个基本问题的认识 基因表达的一个目前知之甚少的方面。因为 C-fos原癌基因mRNA的显著不稳定有助于防止 该基因的致癌转化、鉴定及特性研究 在参与c-fos mRNA衰变的细胞因子中 定义一类新的抑癌基因癌症的可能性。 因此，从拟议研究中学到的知识应该 最终对了解其分子机制有价值。 致癌作用。

In mammalian cells, the c-fos proto-oncogene is a representative of a class of approximately 50-100 growth factor inducible genes, termed immediate early genes, whose transcripts decay rapidly in the cytoplasm with a short half-life of less than 30 min. The instability of this class of mRNA distinguishes it from most mammalian messages, which typically are much more stable with half-lives ranging from hours to days. This proposal focuses on elucidating immediate-early-gene mRNA degradation in mammalian cells, using the c-fos proto-oncogene as a model system. Four important questions are addressed. First, what are the functionally important features of the two major c-fos determinants of mRNA instability? Second, what is the nature of the c-fos coding region determinant of instability? How its destabilizing function is coupled to protein translation? Third, what are the cytoplasmic factors that interact with c- fos instability determinants? Fourth, are the mechanisms by which the c- fos mRNA is targeted for rapid and selective degradation also responsible for the decay of other immediate-early-gene mRNAs? Examination of the structural features of cis-acting determinants of c-fos mRNA and the nature of the c-fos coding region determinant of instability will involve creating defined mutations and fusions of the human c-fos and the rabbit beta-globin genes in vitro, introducing these altered genetic constructs into mouse fibroblasts, and analyzing the decay of the resulting mRNAs in vivo. The identification and characterization of cytoplasmic mRNA degradation factors will involve both reconstituting mRNA decay in an in vitro system and performing in vitro mRNA binding assays. Finally, mRNA decay of three immediate-early-gene mRNAs will be investigated to test for generalization of the decay mechanisms of c-fos mRNA. The results of these studies should enhance our knowledge of a fundamental aspect of gene expression that presently is poorly understood. Because the marked instability of the c-fos proto-oncogene mRNA helps to prevent oncogenic transformation by this gene, identification and characterization of the cellular factors that are involved in the decay of c-fos mRNA has the potential to define a new class of cancer of suppressor genes. Therefore, the knowledge learned form the proposed studies should ultimately be of value to understanding molecular mechanisms of oncogenesis.