Mechanisms of effector activation by the RAS oncogene

Ras癌基因经常与人类癌症相关，并且ras的激活形式在实验系统中具有强大的转化作用。Ras蛋白通过多种效应子控制多种信号通路。Ras激活这些效应子的机制尚不清楚。我们研究了Ras与其效应子/调节子p120 GAP之间的相互作用。我们已经发现，Ras用于调节p120 GAP的催化和调节区域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Nore 1类效应子的分子机制。这些研究的最终目的是设计高度特异性的小分子Ras介导的转化抑制剂。我们发现Ras通过结合Raf上的两个不同位点来激活Raf。两种结合相互作用在产生完全活化的Raf分子中是关键的。我们已经确定了第二Ras结合结构域中的特定残基，这是Ras相互作用所必需的。此外，我们的特点是相互作用的14-3-3和磷脂酰丝氨酸作为辅助因子在Ras介导的激活Raf。我们现在有证据表明，与p120 GAP一样，Ras可以将Raf的C-末端激酶结构域从Raf的N-末端调节结构域的抑制性分子内结合接触中释放出来。这种相互作用似乎是由14-3-3介导的，并且需要脂质辅因子（PS）的结合以充分表现。此外，看来，释放的抑制性分子内相互作用允许相同的结合位点来调节激酶结构域的二聚化事件必不可少的activity.We目前正在研究新的Ras效应Nore 1，以确定是否Ras也采取行动，以不稳定的分子内结合事件或影响二聚化。

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 that 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 studying the novel Ras effector Nore1 to determine if Ras also acts to destabilize intramolecular binding events or to influence dimerization.