The Role of LEM Domain Proteins in Nuclear Function

摘要 人类核纤层蛋白病是由编码核纤层蛋白（NL）的基因突变引起的 proteins.这些蛋白质形成了一个广泛的网络，位于内核之下， 膜的一个统一的疾病模型表明，组织稳态的丧失是由于 无法维持成体干细胞。虽然NL蛋白负责核纤层蛋白病 尽管已经鉴定出了这些蛋白质，但仍不清楚这些蛋白质如何维持健康的干细胞 种群和促进组织稳态。保守的NL家族LEM结构域 （LEM-D）蛋白在构建核结构和NL中起关键作用。LEM-D 蛋白质结合自整合屏障因子（BAF），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，核膜与染色体结合。此外，本发明还提供了一种方法， LEM-D蛋白与BAF相互作用，将基因组系在核周边， 在非分裂细胞中建立抑制的染色质结构域。我们调查的 果蝇LEM-D家族，重点是Otefin，一种LEM-D蛋白， 成体生殖系干细胞（GSC）的存活。otefin突变体GSC携带结构 核纤层异常和核纤层病变细胞共有的染色质改变。我 一个实验室发现，这些突变的GSC死亡是因为一个新的检查点的激活， 使用两种DNA损伤反应（DDR）激酶ATR和Checkpoint的途径 激酶2（Chk2）。虽然otefin突变体GSC携带DNA损伤， 积累依赖于Chk2，表明DNA损伤的结果， 检查点激活。基于这些和其他数据，我们假设NL 变形是ATR和Chk2激活的原因，这一预测得到了以下文献的支持： 新出现的证据表明ATR是细胞结构变形的全球传感器， 件.在这一建议中，提出了两个目标。在目标1中，我们将定义 otefin突变体GSC中ATR/Chk2活化的机制。在目标2中，我们定义Chk 2- 参与GSC死亡的依赖途径。我们希望我们的研究能有广泛的 冲击核形状改变是核纤层蛋白病和早产儿的共同特征。 衰老综合征我们预测，NL检查点的激活可能有助于丢失 干细胞在这些疾病中的作用

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.