Exploring a New Pathway Regulating Mitosis

破坏细胞分裂的分子被广泛用于癌症的治疗。该机制 因为癌细胞比正常细胞更频繁地复制。然而，这种全身中毒 有局限性和副作用伴随着使用传统的抗有丝分裂剂进行了充分的讨论。为 在过去的三年里，我们研究了一种新型的小分子抗有丝分裂-一种天然产物， 重氮酰胺A它在细胞培养中阻断纺锤体组装是非常有效的，并且通过一个 独特的机制该化合物靶向一种以前未知的代谢酶的蛋白水解形式 鸟氨酸5-氨基转移酶（OAT）。这种截短的蛋白质在纺锤体组装过程中起作用， 与小GT3 Ran下游的有丝分裂机制一致。重氮酰胺抑制这种作用 OAT的第二个功能。这一发现的一个特别令人兴奋的方面是，OAT介导的 正常发育不需要纺锤体组装，如OAT缺失小鼠的生存力所证明的。 冗余必须存在，尽管OAT明显支持快速细胞分裂。当合成的重氮酰胺 在裸鼠中静脉内给药，可以使植入的人肿瘤完全消退， 中性粒细胞减少症或体重减轻。这对于小分子抗有丝分裂剂来说是前所未有的。我们的建议旨在 探索这种选择性的起源，并绘制出一种新的调控途径， 在高等真核生物中纺锤体开始组装。我们建议对燕麦进行严格的生化分析 在有丝分裂中的功能以及对缺乏OAT基因产物的动物的遗传背景研究 易患癌症 这项研究与公共卫生有关，因为它可以帮助了解一种新的癌症药物是如何工作的。 并指导其在临床上的应用。

Molecules that disrupt cell division are employed broadly in the treatment of cancer. The mechanism is effective because cancer cells replicate more frequently than normal. However, systemic poisoning of this kind has limits and side effects accompanying the use of conventional anti-mitotics are well discussed. For the past three years, we have studied a new type of small molecule anti-mitotic - a natural product called diazonamide A. It is highly effective at blocking spindle assembly in cell culture, and does so through a unique mechanism. The compound targets a previously unknown proteolyzed form of the metabolic enzyme ornthine 5-amino transferase (OAT). This truncated protein functions in the spindle assembly process, acting in concert with mitotic machinery downstream of the small GTPase Ran. Diazonamide inhibits this unexpected second function of OAT. A particularly exciting aspect of this discovery is that OAT-mediated spindle assembly is not required for normal development, as evidenced by the viability of OAT-null mice. Redundancies must exist, although OAT clearly supports rapid cell division. When a synthetic diazonamide is dosed intravenously in nude mice, one can fully regress implanted human tumors without noticeable neutropenia or weight loss. This is unprecedented for a small molecule anti-mitotic. Our proposal aims to explore the origins of this selectivity and chart what appears to be a new regulatory pathway controlling onset of spindle assemble in higher eukaryotes. We propose a rigorous biochemical analysis of OAT functions in mitosis as well as studies of animals lacking the OAT gene product on genetic backgrounds predisposed to cancer. This research is relevant to public health because it could help understand how a new cancer drug works and guide its use in the clinic.