Shi J, Friedman S, Maciag T
Department of Molecular Biology, Holland Laboratory, American Red Cross, Rockville, Maryland 20855, USA.
J Biol Chem. 1997 Jan 10;272(2):1142-7. doi: 10.1074/jbc.272.2.1142.
The fibroblast growth factor (FGF) prototypes, FGF-1 and FGF-2, lack a signal sequence, but both contain a nuclear localization sequence. We prepared a series of FGF-1 deletion mutants fused to the reporter gene, beta-galactosidase (beta-gal) and determined that a domain between residues 83 and 154 is responsible for FGF-1 cytosol retention in NIH 3T3 cells. Using a series of FGF-beta-gal chimeric proteins prepared by the shuffling of cassette-formatted synthetic FGF prototype genes, we were able to demonstrate that the nuclear localization sequence from the 5'-CUG region of FGF-2 is not able to direct the nuclear association of FGF-1 due to its inability to repress the function of the FGF-1 cytosol retention domain. We also observed that while the FGF-1:beta-gal chimera was released in response to heat shock, the FGF-2:beta-gal protein was not. Further, replacement of the FGF-1 cytosol retention domain with the corresponding domain from FGF-2 repressed the release of the chimeric protein. These data suggest that the specificity of the stress-induced secretion pathway for FGF-1 involves a carboxyl-terminal domain that is absent in FGF-2 and that the FGF-1 secretion pathway does not restrict the release of high molecular weight forms of FGF-1.
成纤维细胞生长因子（FGF）的原型FGF-1和FGF-2缺乏信号序列，但两者都含有核定位序列。我们制备了一系列与报告基因β-半乳糖苷酶（β-gal）融合的FGF-1缺失突变体，并确定83至154位残基之间的结构域负责FGF-1在NIH 3T3细胞中的胞质保留。通过使用由盒式格式的合成FGF原型基因改组制备的一系列FGF-β-gal嵌合蛋白，我们能够证明FGF-2 5'-CUG区域的核定位序列由于无法抑制FGF-1胞质保留结构域的功能，而不能引导FGF-1的核定位。我们还观察到，虽然FGF-1:β-gal嵌合体在热休克后释放，但FGF-2:β-gal蛋白却没有。此外，用FGF-2的相应结构域替换FGF-1的胞质保留结构域可抑制嵌合蛋白的释放。这些数据表明，FGF-1应激诱导分泌途径的特异性涉及FGF-2中不存在的羧基末端结构域，并且FGF-1分泌途径不限制高分子量形式的FGF-1的释放。
