Over-expression of CUG- or AUG-initiated forms of basic fibroblast growth factor in cardiac myocytes results in similar effects on mitosis and protein synthesis but distinct nuclear morphologies.
Over-expression of CUG- or AUG-initiated forms of basic fibroblast growth factor in cardiac myocytes results in similar effects on mitosis and protein synthesis but distinct nuclear morphologies.
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心肌细胞中 CUG 或 AUG 起始形式的碱性成纤维细胞生长因子的过度表达导致对有丝分裂和蛋白质合成的类似影响，但核形态不同。
DOI：
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发表时间：
1994
影响因子：
5
通讯作者：
P. Cattini
中科院分区：
文献类型：
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作者：
K. Pasumarthi;B. Doble;E. Kardami;P. Cattini
同一个mRNA中不同密码子的翻译开始导致多种形式的碱性成纤维细胞生长因子(BFGF)。高分子量的碱性成纤维细胞生长因子利用位于蛋氨酸残基上游的亮氨酸翻译起始点，用于产生18千道尔顿(KDa)形式。虽然外源性18 kDa碱性成纤维细胞生长因子可以刺激包括鸡胚胎心肌细胞在内的多种细胞的DNA合成和增殖，但对高分子量碱性成纤维细胞生长因子的作用却知之甚少。我们对大鼠碱性成纤维细胞生长因子基因进行了修饰，以获得高(22/21.5 kDa)或低(18 KDa)分子量的碱性成纤维细胞生长因子。用蛋白印迹法检测到22/21.5 kDa或18 kDa的碱性成纤维细胞生长因子在鸡胚心肌细胞中的表达。高分子和低分子的碱性成纤维细胞生长因子的表达与(I)总的胸腺嘧啶核苷掺入和心肌细胞标记指数(掺入氚胸苷的心肌细胞核的部分)增加三倍有关；(Ii)细胞数量增加两到三倍；(Iii)蛋白质合成增加八倍；(Iv)肌球蛋白积累减少三倍。用免疫荧光显微镜检测bFGF在心肌细胞培养中的亚细胞定位。高分子量碱性成纤维细胞生长因子的cDNA过度表达导致主要的核碱性成纤维细胞生长因子染色。18 kDa碱性成纤维细胞生长因子过度表达后，胞浆和胞核均可见染色。22/21.5 kDa碱性成纤维细胞生长因子的过度表达与心肌细胞核内形成多个类似浓缩染色质的含DNA的“团块”有关。在高表达18 kDa碱性成纤维细胞生长因子的心肌细胞培养中，没有观察到这些DNA“块”。这些数据表明，高分子形式和低分子形式的碱性成纤维细胞生长因子的过度表达可以刺激心肌细胞的增殖能力，减少肌球蛋白的积聚。然而，这些形式具有不同的亚细胞定位，并在细胞核中具有不同的生物学功能。
Initiation of translation from alternate codons in the same mRNA results in multiple forms of basic fibroblast growth factor (bFGF). High molecular weight species of bFGF make use of leucine translation initiation sites located upstream of the methionine residue used to produce the 18 kiloDalton (kDa) form. Although the addition of exogenous 18 kDa bFGF is known to stimulate DNA synthesis and proliferation of several cell types including embryonic chicken cardiac myocytes, little is known about the role of high molecular weight forms of bFGF. We modified the rat bFGF cDNA to yield high (22/21.5 kDa) or low (18 kDa) molecular weight species of bFGF. Expression of 22/21.5 kDa or 18 kDa bFGF in transfected embryonic chicken ventricular myocyte cultures was confirmed by protein blotting. Expression of both high and low molecular weight species of bFGF was associated with (i) a three-fold increase in overall thymidine incorporation as well as cardiomyocyte labelling index (fraction of cardiomyocyte nuclei incorporating tritiated thymidine); (ii) a two- to three-fold increase in cell number; (iii) an eight-fold increase in protein synthesis; and (iv) a three-fold decrease in myosin accumulation. Subcellular localization of bFGF in the transfected myocyte cultures was also assessed by immunofluorescence microscopy. Over-expression of cDNAs yielding high molecular weight bFGF resulted in predominantly nuclear bFGF staining. By contrast, both cytoplasmic and nuclear staining were observed following over-expression of 18 kDa bFGF. Over-expression of 22/21.5 kDa bFGF was associated with the formation of multiple DNA-containing "clumps" resembling condensed chromatin in cardiac myocyte nuclei. These DNA "clumps" were not observed in cardiac myocyte cultures over-expressing 18 kDa bFGF. These data indicate that over-expression of high as well as low molecular weight forms of bFGF can stimulate cardiac myocyte proliferative potential and decrease myosin accumulation. However, these forms possess distinct subcellular localizations and can have different biological functions in the nucleus.