DNA REPAIR SIGNALING BY NOVEL POLYUBIQUITIN CHAINS

描述(由申请人提供)： 在保守的RAD6 DNA损伤耐受途径中，通过Ub-K63连接的多聚泛素(PolyUb)链是一个非蛋白水解性信号，而通过Ub-K48连接的多聚泛素(PolyUb)链则扮演不同的角色，作为蛋白酶体蛋白分解的信号。这些和其他观察结果表明，Ub组装成不同类型的PolyUb链是一种通过泛素在信号传递中赋予功能多样性的机制。K63-1连接的PolyUb链在DNA损伤耐受性中的信号在酵母和人类之间是保守的。但是，尽管最近取得了进展，这种新信号的分子功能仍然知之甚少。拟议的研究通过涉及生化和分子遗传学方法的机械聚焦方法来针对这一问题。具体目标是1)阐明K63-1连接的PolyUb链(目标1-3)对DNA损伤信号的具体机制；2)发现许多蛋白质(UBA结构域；目标4)中存在的一个小的Ub结合元件识别连锁特异性链的原理。我们的研究结果可能有助于揭示癌症和其他由基因组不稳定导致的疾病的原因。我们的发现也可能提出抑制RAD6途径的方法，这可能在临床上对化疗或放射增敏有益。最后，我们对UBA结构域识别(PolyUb)Ub的分子探索应该有助于建立基本的信号识别原理，并可能导致更好地理解泛素在信号转导中的多样性和特异性。

DESCRIPTION (provided by applicant): Polyubiquitin (polyUb) chains linked through Ub-K63 act as a non-proteolytic signal in the conserved RAD6 DNA damage tolerance pathway, while chains linked through Ub-K48 play a different role, acting as a signal for proteasome proteolysis. These and other observations suggest that the assembly of Ub into different types of polyUb chains is a mechanism for imparting functional diversity in signaling by ubiquitin. Signaling by K63-1inked polyUb chains in DNA damage tolerance is conserved from yeast to man. But despite recent advances, the molecular function of this novel signal remains poorly understood. The proposed research targets this question through mechanistically focused approaches involving biochemical and molecular genetic methods. The specific goals are 1) to elucidate the specific mechanism of DNA damage signaling by K63-1inked polyUb chains (Aims 1-3) and 2) to discover the principles that underlie linkage-specific chain recognition by a small Ub-binding element that occurs in numerous proteins (the UBA domain; Aim 4). The results of our studies may shed light on the causes of cancer and other diseases promoted by genomic instability. Our findings may also suggest ways to inhibit the RAD6 pathway, which could be clinically beneficial in chemotherapy or radiosensitization. Finally, our molecular exploration of (poly)Ub recognition by UBA domains should help to establish fundamental signal recognition principles and may lead to a better appreciation of diversity and specificity in signaling by ubiquitin.