Mechanisms of effector activation by the RAS oncogene

Ras癌基因经常与人类癌症相关，在实验系统中，Ras的活化形式具有强大的转化能力。Ras蛋白通过多种效应物控制多种信号通路。这些效应物被Ras激活的机制尚不清楚。我们研究了Ras与其效应/调节因子p120 GAP之间的相互作用。我们发现Ras可以调节p120 GAP的催化区和调控区之间的分子间相互作用。我们也在研究Ras蛋白激活Raf激酶和Nore1类效应物的分子机制。这些研究的最终目的是允许设计高度特异性的Ras介导转化的小分子抑制剂。

Ras oncogenes are frequently associated with human cancer and activated forms of ras are powerfully transforming in experimental systems. Ras proteins control multiple signaling pathways via multiple effectors. The mechanisms by which those effectors are activated by Ras remain unclear. We have investigated the interaction between Ras and its effector/regulator p120 GAP. We have found that Ras serves to modulate an interamolecular interaction between the catalytic and the regulatory regions of p120 GAP. We are also investigating the molecular mechanisms by which the Ras proteins activate the Raf kinase and Nore1 class of effectors. The ultimate aim of these studies is to allow the design of highly specific small molecule inhibitors of Ras mediated transformation. We have found that Ras activates Raf by binding to two distinct sites on Raf. Both binding interactions are crtitical in generating a fully activated Raf molecule. we have identified specific residues within the second Ras binding domain which are essential for Ras interaction. Moreover, we have characterized the interplay of 14-3-3 and Phosphatidylserine as co-factors in the Ras mediated activation of Raf. We now have evidence that, as with p120 GAP, Ras serves to release the c-terminal kinase domain of Raf from inhibitory, intramolecular binding contacts in the n-terminal, regulatory domain of Raf. This interaction appears to mediated by 14-3-3 and requires the binding of a lipid co-factor (PS) for full manifesrtation. Moreover, it appears that the release of the inhibitory intramolecular interaction allows the same binding sites to modulate a kinase domain dimerization event essential for activity. We are currently investigating the novel Ras effector Nore1 to determine if it exhinbits a conserved mechanism of regulation.