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Nore1类效应子的分子机制。这些研究的最终目的是允许设计Ras介导的转化的高度特异性的小分子抑制剂。 我们已经发现Ras通过结合Raf上的两个不同位点来激活Raf。这两种结合相互作用对于产生完全活化的Raf分子至关重要。我们已经鉴定了第二Ras结合结构域中Ras相互作用所必需的特定残基。此外，我们已经表征了14 - 3 - 3和磷脂酰丝氨酸作为Ras介导的Raf活化中的辅因子的相互作用。我们现在有证据表明，与p120 GAP一样，Ras可以从Raf的N-末端调节结构域中的抑制性分子内结合接触中释放Raf的C-末端激酶结构域。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，似乎释放抑制性分子内相互作用允许相同的结合位点调节活性所必需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，以确定它是否表现出保守的调控机制。

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.