Mitotic exit network and human cancer

描述（由申请人提供）：癌症遗传不稳定的主要原因之一是有丝分裂错误导致子细胞之间遗传物质的不平等分离。许多有丝分裂事件和监控这些事件的检查点在分子水平上还没有被理解。在有丝分裂后期发生的事件尤其如此，在有丝分裂后期向末期转变时，细胞将姐妹染色单体脱密并重新组装细胞核。在酿酒酵母中，介导这些事件的途径被称为有丝分裂退出网络（MEN）。在人类细胞中，MEN通路尚未被表征。然而，人类蛋白激酶Lats 1与酵母MEN激酶具有高度的序列相似性。Lats 1与有丝分裂有关，但其确切功能尚不清楚。然而，Latsl显然与癌症的发展有关；在果蝇、小鼠和人类中，Lats 1是一种公认的肿瘤抑制蛋白。我们假设Lats 1在人类细胞的MEN通路中起作用，并且该通路的解除导致遗传不稳定（通过杂合性损失分析测量）。这一假设将通过执行以下具体目标来解决：

DESCRIPTION (provided by applicant): One of the major causes of genetic instability in cancer is errors in mitosis leading to unequal segregation of the genetic material between daughter cells. Many of the mitotic events and the checkpoints that monitor these events are yet to be understood at the molecular level. This is particularly true for the events that occur in late mitosis at the anaphase to telophase transition, when cells decondense their sister chromatids and reassemble their nuclei. In S. cerevisiae, the pathway that mediates these events is referred to as the mitotic exit network (MEN). In human cells a MEN pathway has not been characterized. However, a human protein kinase, Lats 1, has high sequence similarity to a yeast MEN kinase. Lats 1 has been implicated in mitosis, but its precise function is unclear. Nevertheless, Latsl is clearly linked to cancer development; in flies, mice and humans, Lats 1 is a well-established tumor suppressor protein. We hypothesize that Lats 1 functions in a MEN pathway in human cells and that deregulation of this pathway leads to genetic instability (as measured by loss-of-heterozygosity analysis). This hypothesis will be addressed by performing the following Specific Aims: 1. Establish that Lats 1 is the human ortholog of the S. cerevisiae Dbf2 MEN kinase. We will examine if Lats 1 shares with Dbf2 the ability to be regulated by Mob proteins. We will further examine whether Lats 1 functions in the MEN pathway in human cells using an siRNA approach and dominant negative mutants. 2. Establish that Lats 1 is regulated by hDmal. In S. pombe the MEN kinases are regulated by Dmal, a putative ubiquitin ligase. We will examine if human Lats 1 is regulated by hDmal, a ubiquitin ligase that has high sequence similarity with yeast Dmal. 3. Establish that deregulation of LATS 1 and hDmal increases the frequency of loss-of-heterozygosity (LOH). LOH is clearly involved in cancer development and progression. Thus, these studies will help identify the molecular basis for the tumor suppressor function of Lats 1.