REGULATION AND ONCOGENIC FUNCTION OF GROWTH FACTOR FGF4

我们最近从一个病人的DNA中分离出了一个转化基因 慢性粒细胞白血病的NIH3T3细胞病灶形成试验。 负责转化的序列已被克隆， 表征了 转化基因已被鉴定为成纤维细胞 生长因子4（FGF4）。 FGF4的表达仅限于 未分化的胚胎干细胞和胚胎癌细胞， 在体细胞组织中表达。 FGF4基因的编码序列 （位于11号染色体上）已经融合到RNA处理信号， 15号染色体上的一个未知基因 FGF4的转化， 先前描述的研究是表达失调的结果， 而不是编码序列的突变。 因此， 探讨FGF4表达的调控机制。 巧合的是， 内源性FGF4的表达在NIH3T3细胞中被抑制， 外源添加的正常基因的拷贝被表达并能够 诱导转化。 拟议研究的目标有三个方面。 首先，我们希望进一步研究和探讨的机制 局部控制FGF4的表达。 具体来说，要确定发起人的日期 在所有测试的细胞系中均显示无活性，除非与 激活3'增强子序列。 功能性启动子结构域的研究 因此被证明是困难的。 使用瞬时报告基因分析系统 （荧光素酶），其比先前使用的系统（CAT）更敏感 通过其他人，我们已经确定了5'端启动子的活性结构域， FGF4的侧翼序列，并已显示启动子在两个 胚胎癌细胞（F9），其允许FGF 4表达， 而HeLa细胞则不然。 我们希望进一步开展这些研究， 表征启动子和增强子内的功能结构域 序列，并研究这些序列如何相互作用，以控制 FGF4的局部表达。 其次，根据以往的数据显示， 携带FGF4基因的粘粒克隆正在转化， 内源性基因是沉默的，我们认为FGF4表达的可能性， 也可以从远距离基因座调节。 我们会调查的 通过将含有以下的YAC克隆转移到NIH3T3细胞中的可能性 FGF4基因。 因此，这些克隆体将包含更多的 与先前描述的克隆相比，FGF4基因侧翼的序列。 如果 YAC的转移产生正常而非转化的细胞集落 形态学，可以推断，一个假定的抑制基因座已被 共转移，然后进一步表征该基因座。 第三， 对FGF4激活的基因知之甚少 诱导NIH3T3细胞转化。 我们将尝试识别和 通过利用最近的基于PCR的新方法来表征这些基因， 其允许鉴定和克隆来自差异表达的cDNA， 表达的基因。

We have recently isolated a transforming gene from the DNAS of a patient with chronic myeloid leukemia using the NIH3T3 cell focus formation assay. The sequences responsible for transformation have been cloned and characterized. The transforming gene has been identified as fibroblast growth factor 4 (FGF4). Expression of FGF4 is restricted to undifferentiated embryonic stem and embryonal carcinoma cells and is not expressed in somatic tissue. The coding sequences of the FGF4 gene (located on chromosome 11) have been fused to RNA processing signals from an unidentified gene on chromosome 15. Transformation by FGF4 in this and previously described studies is the result of deregulated expression rather than mutation of the coding sequences. It is therefore of value to investigate the mechanism of regulation of FGF4 expression. Paradoxically, expression of endogenous FGF4 is suppressed in NIH3T3 cells yet an exogenously added copy of the normal gene is expressed and capable of inducing transformation. The goals of the proposed study are threefold. Firstly we wish to further previous studies and investigate the mechanism of local control of FGF4 expression. Specifically, to date the promoter has been shown to be inactive in all cell lines tested unless linked to an activating 3' enhancer sequence. Study of functional promoter domains has thus proven difficult. Using a transient reporter assay system (luciferase) which is more sensitive than the system (CAT) used previously by others, we have identified active promoter domains within the 5' flanking sequence of FGF4 and have shown the promoter to be active in both embryonal carcinoma cells (F9) which are permissive for FGF4 expression and HeLa cells which are not. We wish to further these studies and characterize functional domains both within the promoter and the enhancer sequence and to investigate how such sequences might interact to control local expression of FGF4. Secondly, based on previous data demonstrating that cosmid clones harboring the FGF4 gene are transforming while the endogenous gene is silent, we suggest the possibility that FGF4 expression may also be regulated from a distant locus. We will investigate this possibility by the transfer into NIH3T3 cells of YAC clones containing the FGF4 gene. These clones will therefore contain substantially greater sequence flanking the FGF4 gene than clones previously described. If transfer of YACs produce cell colonies of normal rather than transformed morphology, it may be inferred that a putative suppressor locus has been co-transferred and this locus will then be further characterized. Thirdly, little is known about the genes which are activated in response to FGF4 induced transformation of NIH3T3 cells. We will attempt to identify and characterize these genes by utilizing a recent and novel PCR based method which allows the identification and cloning of cDNA from differentially expressed genes.