Mechanisms of effector activation by the RAS oncogene

Ras癌基因经常与人类癌症相关，激活形式的ras在实验系统中正在发生强有力的转化。RAS蛋白通过多个效应器调控多条信号通路。RAS激活这些效应器的机制尚不清楚。我们研究了RAS与其效应器/调节子p120间隙之间的相互作用。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。我们还在研究RAS蛋白激活Raf激酶和Nore1类效应器的分子机制。这些研究的最终目的是设计高度特异的RAS介导转化的小分子抑制剂。 我们已经发现RAS通过与Raf上的两个不同的位点结合来激活Raf。这两种结合作用在产生完全激活的Raf分子方面都是至关重要的。我们已经在第二个RAS结合域中确定了对RAS相互作用至关重要的特定残基。此外，我们还表征了14-3-3和磷脂酰丝氨酸的相互作用是RAS介导的Raf激活的辅助因素。我们现在有证据表明，与p120 GAP一样，RAS可以从Raf的n端调节域中的抑制性分子内结合接触中释放Raf的c末端激动域。这种相互作用似乎是由14-3-3介导的，需要脂质辅助因子(PS)的结合才能充分表现出来。此外，抑制的分子内相互作用的释放似乎允许相同的结合位点调节对活性至关重要的激酶结构域二聚化事件。 我们目前正在研究新的RAS效应器Nore1，以确定它是否阻碍了一种保守的调节机制。

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 manifestation. 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.