Ichiba T, Hoshi Y, Eto Y, Tajima N, Kuraishi Y
Department of Internal Medicine (3), Jikei University, School of Medicine, Tokyo, Japan.
FEBS Lett. 1999 Aug 20;457(1):85-9. doi: 10.1016/s0014-5793(99)01012-1.
Three groups of Rap1-specific guanine nucleotide exchange factors including C3G, CalDAG-GEFI, and Epac/cAMP-GEFI/II have been identified to date. In the present study, we report a new Rap1 guanine nucleotide exchange factor which we have named GFR (guanine nucleotide exchange factor for Rap1). GFR shows close sequence similarity to EPAC/cAMP-GEFI/II although GFR lacks a cAMP binding domain and contains a nuclear localization signal. We demonstrated that GFR can activate Rap1 but not H-Ras in 293T cells and that the cdc25 domain of GFR is required for the activation of Rap1. Northern blot analysis suggested that GFR mRNA is strongly expressed in the brain. In transfected HeLa cells, GFR has been found to be localized in the nuclei.
迄今为止，已鉴定出三组Rap1特异性鸟嘌呤核苷酸交换因子，包括C3G、CalDAG-GEFI和Epac/cAMP-GEFI/II。在本研究中，我们报告了一种新的Rap1鸟嘌呤核苷酸交换因子，我们将其命名为GFR（Rap1的鸟嘌呤核苷酸交换因子）。尽管GFR缺乏cAMP结合结构域并含有核定位信号，但它与EPAC/cAMP-GEFI/II具有密切的序列相似性。我们证明，GFR可在293T细胞中激活Rap1，但不能激活H-Ras，并且GFR的cdc25结构域是激活Rap1所必需的。Northern印迹分析表明，GFR mRNA在脑中强烈表达。在转染的HeLa细胞中，已发现GFR定位于细胞核中。
