van Leeuwen F N, van der Kammen R A, Habets G G, Collard J G
The Netherlands Cancer Institute, Antoni van Leeuwenhoekhuis, Division of Cell Biology, Amsterdam, The Netherlands.
Oncogene. 1995 Dec 7;11(11):2215-21.
We have recently identified the invasion-inducing Tiam1 gene by proviral insertional mutagenesis. The Tiam1 protein shares a Dbl homology (DH) domain with an increasing number of oncoproteins, some of which have been shown to function as GDP dissociation stimulators (GDS) for small GTPases of the Rho family. In vitro and in vivo analyses indicate that Tiam1 activates the Rho like GTPase Rac1. Here we have analysed the consequences of overexpression of several mutant Tiam1 proteins in NIH3T3 fibroblasts. Similar to other proteins containing a DH domain, N-terminal truncation of the Tiam1 protein activates its oncogenic potential, establishing Tiam1 as a proto-oncogene. In addition, we show the sequences N-terminal of the catalytic DH domain are required for morphological transformation accompanied by the formation of membrane ruffling, but not for the induction of an oncogenic phenotype. Overexpression of constitutively active Rac1 (V12Rac1) in NIH3T3 cells produces a similar oncogenic phenotype, suggesting that the oncogenic effects of Tiam1 are a consequence of Rac activation.
我们最近通过前病毒插入诱变鉴定出了诱导侵袭的Tiam1基因。Tiam1蛋白与越来越多的癌蛋白共享一个Dbl同源（DH）结构域，其中一些已被证明可作为Rho家族小GTP酶的GDP解离刺激剂（GDS）发挥作用。体外和体内分析表明，Tiam1可激活Rho样GTP酶Rac1。在此，我们分析了几种突变Tiam1蛋白在NIH3T3成纤维细胞中过表达的后果。与其他含有DH结构域的蛋白类似，Tiam1蛋白的N端截短激活了其致癌潜能，确立了Tiam1作为原癌基因的地位。此外，我们表明，催化DH结构域N端的序列是伴随膜皱褶形成的形态转化所必需的，但不是诱导致癌表型所必需的。在NIH3T3细胞中组成型激活的Rac1（V12Rac1）过表达产生了类似的致癌表型，表明Tiam1的致癌作用是Rac激活的结果。
