Integrating chromatin structure and global chromosome dynamics

DNA的作用是存储个体的遗传信息，以便在正常生长和发育期间使用，并在细胞的不同分裂期间被准确复制。人类细胞含有总长约2米的DNA，必须包装在直径只有0.01毫米的细胞核内。重要的是，DNA必须以一种便于各种关键过程访问的方式组织起来。它所包含的信息必须易于阅读(转录)，这样细胞才能快速产生蛋白质。它必须在细胞分裂(有丝分裂)和有性繁殖(减数分裂)期间容易复制(DNA复制)和准确分离。此外，可能发生的任何断裂、打结或缠结都可以修复(DNA修复)，这也是至关重要的。DNA与不同的蛋白质结合形成一种称为染色质的核蛋白复合体。这使得在保持对遗传信息的访问的同时，将裸露的DNA适合于细胞核内所需的紧凑成为可能。染色质被分成组成染色体的各个结构。在细胞分裂的过程中，当单个染色体被复制时，染色体凝聚是必要的，以确保它们的准确分布。在细胞周期或配子产生过程中，染色体凝聚的失控会导致细胞死亡、癌症和染色体的不正确分离。将DNA包装到染色体中涉及到不同程度的紧凑。基本结构是核小体，由裸露的DNA包裹在称为组蛋白的蛋白质核心上形成。核小体沿着DNA排列，形成直径10 nm的纤维，就像绳子上的珠子。尽管过去的印象是核小体是静态的结构，但现在，核小体被认为是高度动态的组合。这种有组织结构的变化是通过组蛋白修饰、模拟因子和组蛋白交换来促进的。核小体纤维通过缠绕成30 nm的纤维进一步致密，其结构仍有争议。这种纤维另外排列成环状，连接到一个被称为染色体支架的多蛋白质轴上。尽管组蛋白和其他染色体相关蛋白的生物化学已经得到了深入的研究，但它们之间的相互作用实现染色体凝聚的机制仍然知之甚少。我的研究项目旨在揭示不同水平的DNA紧致结构和成分对细胞核内染色体凝聚的生物学意义。正确的染色体凝聚对于遗传信息的稳定性是至关重要的。这个项目将有助于理解不同的重要和有趣的主题，如细胞分裂、癌症、干细胞、染色体改变、生育和植物育种。参与染色体凝聚的关键蛋白在整个真核进化过程中都是保守的，这表明它们可能具有与物种无关的基本作用。我将使用拟南芥，这是一种用于遗传学和分子生物学基础研究的植物模型生物，是一个良好的实验系统，没有任何与动物工作相关的伦理问题。此外，我还开发了一系列分子细胞遗传学技术，为研究拟南芥的染色体动力学做出了贡献。我最近发现了令人兴奋的证据，一些组蛋白和染色体支架突变体在不同程度上影响了染色体凝聚。因此，我想对这些和其他相关蛋白质进行彻底的分析。我建议使用一种结合新的高分辨率细胞遗传学技术、突变特征、蛋白质组学分析和数学模型的多学科方法来解决导致准确染色体凝集的单个染色质成分的复杂相互作用。

The role of DNA is to store an individual's genetic information such that it can be used during normal growth and development and be accurately copied during the different divisions of the cell. Human cells contain DNA totalling about 2 m in length that has to be packed within the cell nucleus which is only 0.01 mm in diameter. Importantly, the DNA must be organised in such a way that it is readily accessible for a variety of crucial processes. The information it contains must be easily read (transcription) so that the cell can rapidly produce proteins. It must be readily duplicated (DNA replication) and accurately separated during cell division (mitosis) and sexual reproduction (meiosis). Also, it is essential that any break, knot or tangle that might occur can be repaired (DNA repair). DNA associates with different proteins forming a nucleo-protein complex called chromatin. This enables the compaction necessary to fit the naked DNA inside the cell nucleus whilst maintaining access to the genetic information. The chromatin is divided into individual structures constituting chromosomes. During the process of cell division when the individual chromosomes have been duplicated chromosome condensation is necessary to ensure their accurate distribution. Miss-regulation of chromosome condensation can lead to cell death, cancer and improper chromosome segregation during cell cycle or during the production of gametes. There are different levels of compaction involved in packaging DNA into chromosomes. The basic structure is the nucleosome, formed by wrapping naked DNA around a core of proteins known as histones. The nucleosomes are arranged along the DNA forming a 10nm diameter fibre, likened to beads on a string. Despite the old impression that nucleosomes were static structures, nowadays, a nucleosome is considered as a highly dynamic assemblage. Changes to this organised structure are facilitated through histone modifications, modelling factors and exchange of histone proteins. The nucleosomal fibre is further compacted by winding it into a 30 nm fibre whose structure remains controversial. This fibre is additionally arranged into loops that are attached to a multi-protein axis called the chromosome scaffold. Although the biochemistry of histones and other chromosome-associated proteins has been studied intensively, their interactions to achieve chromosome condensation are still poorly understood. My research project aims to unravel the biological significance that the different levels of DNA compaction structures and components have on chromosome condensation in the nucleus. The correct chromosome condensation is essential for the stability of the genetic information. This project will contribute to the understanding of different important and interesting subjects like cell division, cancer, stem cells, chromosome alterations, fertility and plant breeding. The key proteins involved in chromosome condensation are conserved throughout eukaryotic evolution indicating that they are likely to have fundamental roles that are species-independent. I will be using Arabidopsis thaliana, a plant model organism for basic research in genetics and molecular biology and a good experimental system without any of the ethical issues related to working with animals. Furthermore, I have developed a range of molecular cytogenetic techniques that have contributed to the study of chromosome dynamics in Arabidopsis. I have recently found exciting evidence that some histone and chromosome scaffold mutants are affected in chromosome condensation at different levels. Thus, I would like to conduct a thorough analysis of these and other related proteins. I propose to use a multidisciplinary approach combining new high-resolution cytogenetic techniques, mutant characterisation, proteomic analysis, and mathematical models to resolve the complicated interactions of individual chromatin components that result in accurate chromosome condensation.