The Role of LEM Domain Proteins in Nuclear Function

摘要 人类椎板病是由编码核板(NL)的基因突变引起的 蛋白质。这些蛋白质形成了一个位于内核下方的广泛网络。 薄膜。一个统一的疾病模型表明，组织动态平衡的丧失是由于 未能维持成人干细胞。尽管NL蛋白与椎板病变有关 目前尚不清楚这些蛋白质是如何维持干细胞健康的 并促进组织动态平衡。LEM-整环的守恒NL族 (Lem-D)蛋白在构建核结构和NL中起着关键作用。LEM-D 蛋白质结合屏障自整合因子(BAF)，这是一种保守的双链DNA 和组蛋白结合蛋白。LEM-D蛋白与BAF靶标的相互作用 在有丝分裂后的核组装过程中，核膜向染色体转移。此外, LEM-D蛋白与BAF相互作用，将基因组连接到核周，并 在非分裂细胞中建立被抑制的染色质结构域。我们调查了 果蝇LEM-D家族，关注Otefin，一种LEM-D蛋白，是 成年生殖系干细胞(GSCs)的存活。Otefin突变型GSCs携带结构 椎板病变细胞所共有的NL畸形和染色质改变。我的 实验室发现，这些突变的GSC死亡是因为激活了一个新的检查点 使用两种DNA损伤反应(DDR)激酶ATR和Checkpoint的途径 蛋白激酶2(Chk2)。尽管Otefin突变的GSC会造成DNA损伤，但 积累依赖于Chk2，证明DNA损伤是由 检查点激活。根据这些和其他数据，我们假设NL 变形是激活ATR和Chk2的原因，这一预测得到了 ATR是细胞结构变形的全球性传感器的新证据 组件。在这项建议中，提出了两个目标。在目标1中，我们将定义 Otefin突变的GSCs中ATR/Chk2激活的机制。在目标2中，我们定义了Chk2- 参与GSC死亡的依赖通路。我们希望我们的学习将会有广泛的 冲击力。核形态改变是椎板病和早产儿的共同特征 衰老综合症。我们预测，民族解放阵线检查站的激活可能会导致损失 干细胞在这些疾病中的维持。

ABSTRACT Human laminopathies are caused by mutations in genes encoding nuclear lamina (NL) proteins. These proteins form an extensive network that lies beneath the inner nuclear membrane. A unifying disease model suggests that lost tissue homeostasis is due to a failure to maintain adult stem cells. Although NL proteins responsible for laminopathies have been identified, it remains unclear how these proteins maintain healthy stem cell populations and promote tissue homeostasis. The conserved NL family of LEM-domain (LEM-D) proteins play a critical role in building nuclear structure and the NL. LEM-D proteins bind Barrier-to-Autointegration Factor (BAF), a conserved double stranded DNA and histone binding protein. Interactions between LEM-D proteins and BAF target nuclear membranes to chromosomes during nuclear assembly after mitosis. In addition, LEM-D proteins interact with BAF to tether the genome to the nuclear periphery and establish repressed chromatin domains in non-dividing cells. We investigate the Drosophila LEM-D family, focusing on Otefin, a LEM-D protein that is required for survival of adult germline stem cells (GSCs). The otefin mutant GSCs carry structural deformities of the NL and chromatin changes that are shared with laminopathic cells. My lab discovered that these mutant GSCs die because of activation of a novel checkpoint pathway that uses two DNA damage response (DDR) kinases, ATR and Checkpoint kinase 2 (Chk2). Although otefin mutant GSCs carry DNA damage, damage accumulation depends upon Chk2, demonstrating that DNA damage results from checkpoint activation. Based on these and other data, we hypothesize that NL deformation is responsible for activation of ATR and Chk2, a prediction supported by emerging evidence that ATR is a global sensor of structural deformities of cellular components. In this proposal, two Aims are proposed. In Aim 1, we will define the mechanism of ATR/Chk2 activation in otefin mutant GSCs. In Aim 2, we define Chk2- dependent pathways involved in GSC death. We expect our studies will have a broad impact. Nuclear shape changes are shared features of laminopathies and premature aging syndromes. We predict that activation of the NL checkpoint might contribute to lost stem cell maintenance in these diseases.