Pasumarthi K B, Jin Y, Cattini P A
Department of Physiology, University of Manitoba, Winnipeg, Canada.
J Neurochem. 1997 Mar;68(3):898-908. doi: 10.1046/j.1471-4159.1997.68030898.x.
Basic fibroblast growth factor (FGF-2) is abundant in the developing and adult brain and has been linked with the origin and growth of neuronal and glial cells. Glial cells produce high levels of FGF-2, stimulating autocrine growth as well as the survival and function of neurons in a paracrine manner. Abnormal levels of FGF-2 have been linked with Alzheimer's, Huntington's, and Parkinson's diseases. Recent evidence has suggested that a component of the mitogenic response of glial cells is exerted on FGF-2 at the transcriptional level. To assess transcriptional regulation of this potent growth factor, we cloned a 1.4-kb genomic fragment containing the rat FGF-2 promoter region. DNA blotting results indicated that the rat FGF-2 gene exists as a single copy in the genome. The promoter region contains no TATA box but appears to rely instead on multiple GC-rich start sites (P0, P1, and P2) for transcription initiation in rat brain as well as C6 glioma cells. One of these sites (P0) was located within four nucleotides of the reported 5' end of the rat brain cDNA and constituted part of a consensus Egr-1 binding site (5'-GCGGGGGCG-3'). Transcription from this site could be stimulated in C6 glioma cells in response to phorbol ester treatment. The induction of a "new" site (P1) with phorbol ester also suggested a mechanism to explain the discrepancy between the reported "starts" for the ovarian versus brain cDNAs. A hybrid luciferase gene directed by rat FGF-2 5'-flanking DNA (-1,058/+54) was expressed in rat glioma C6, heart myoblast H9c2, and human astrocytoma U87-MG cells after gene transfer. The level of transfected FGF-2 promoter activity was higher in glial cells (C6 and U87-MG) compared with nonglial (H9c2) cells. Also, expression of this hybrid FGF-2/luciferase gene was increased in response to phorbol ester or serum treatment of C6 cells. Deletion analysis revealed the presence of both positive and negative regulatory regions that are involved in the transcriptional control of rat FGF-2 gene by mitogenic stimuli.
碱性成纤维细胞生长因子（FGF - 2）在发育中的大脑和成年大脑中含量丰富，并且与神经元和神经胶质细胞的起源及生长有关。神经胶质细胞产生高水平的FGF - 2，以自分泌方式刺激自身生长，并以旁分泌方式影响神经元的存活和功能。FGF - 2水平异常与阿尔茨海默病、亨廷顿病和帕金森病有关。最近的证据表明，神经胶质细胞促有丝分裂反应的一个组成部分是在转录水平上作用于FGF - 2。为了评估这种强效生长因子的转录调控，我们克隆了一个包含大鼠FGF - 2启动子区域的1.4 kb基因组片段。DNA印迹结果表明，大鼠FGF - 2基因在基因组中以单拷贝形式存在。启动子区域没有TATA盒，而是似乎依赖多个富含GC的起始位点（P0、P1和P2）在大鼠脑以及C6胶质瘤细胞中起始转录。其中一个位点（P0）位于大鼠脑cDNA报道的5'端的四个核苷酸内，构成了一个共有Egr - 1结合位点（5'-GCGGGGGCG-3'）的一部分。在C6胶质瘤细胞中，佛波酯处理可刺激该位点的转录。佛波酯诱导一个“新”位点（P1）也提示了一种机制，可解释卵巢cDNA与脑cDNA报道的“起始”之间的差异。由大鼠FGF - 2 5'侧翼DNA（-1,058 / +54）指导的杂交荧光素酶基因在基因转移后在大鼠胶质瘤C6、心肌母细胞H9c2和人星形细胞瘤U87 - MG细胞中表达。与非神经胶质细胞（H9c2）相比，转染的FGF - 2启动子活性在神经胶质细胞（C6和U87 - MG）中更高。此外，用佛波酯或血清处理C6细胞后，这种杂交FGF - 2/荧光素酶基因的表达增加。缺失分析揭示了存在正调控区和负调控区，它们参与有丝分裂刺激对大鼠FGF - 2基因的转录控制。
