Mechanistic dissection of HP1 mediated heterochromatin

HP1介导的异染色质的机制剖析

基本信息

批准号：
8711780
负责人：
GEETA J NARLIKAR
金额：
$ 42.6万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-05-01 至 2018-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8711780
关键词：
Address Adopted Affect Behavior Biochemical Biological Biological Models Cells Chromatin Chromatin Structure Chromosome Segregation Complex Cryoelectron Microscopy DNA Development Dissection Equilibrium Fission Yeast Foundations Gene Activation Gene Silencing Genetic Recombination Genetic Transcription Genome Goals Heterochromatin Histone H3 In Vitro Ligands Link Lysine Malignant Neoplasms Mediating Methods Molecular Molecular Conformation Myeloid Leukemia Nucleosomes Play Post-Translational Protein Processing Process Property Protein Isoforms Proteins Recruitment Activity Regulation Role Schizosaccharomyces pombe Proteins Structure Testing Therapeutic Intervention Work analytical ultracentrifugation base chromatin protein dimer in vivo in vivo Model inhibitor/antagonist leukemia malignant breast neoplasm public health relevance

项目摘要

DESCRIPTION (provided by applicant): The spread of heterochromatin is crucial for heritably silencing large regions of the genome and consequently for generating and maintaining cell identity during development. Illegitimate gene activation from loss of heterochromatin spread is strongly linked to invasive breast cancers while illegitimate gene silencing from aberrant heterochromatin spread is strongly linked to myeloid leukemias. In addition to gene silencing, heterochromatin plays crucial roles in recombination and chromosome segregation. At the core of the most conserved form of heterochromatin is the complex formed between HP1 proteins and chromatin methylated on lysine 9 of histone H3 (H3K9me3). The following key roles have been attributed to HP1 proteins in heterochromatin function: (1) The HP1-nucleosome complex is hypothesized to recruit effector molecules to H3K9me3 chromatin. Paradoxically, effectors that both, enable as well as restrict further heterochromatin spread are recruited. The balance between these opposing activities is thought to dictate the functions and stability of the assembled heterochromatin. (2) HP1 proteins are hypothesized to directly mediate the spread of heterochromatin by oligomerizing across multiple nucleosomes. (3) HP1 proteins are hypothesized to condense chromatin and thereby directly reduce the access of DNA to the transcription machinery. Despite the centrality of these properties to the in vivo functions of heterochromatin, the molecular basis for how HP1 accomplishes these roles is poorly understood. We have made the new discovery that Swi6, the major S. pombe HP1 isoform, switches from an auto-inhibited state to a spreading-competent state in a manner that depends on recognition of H3K9me3 and additional features of a nucleosome. We will build on these and additional results to address the following questions in the S. pombe model system: (i) how do HP1 proteins interact with different effectors, (iii) why do different HP1 isoforms have different functions, (iii) how do HP1 proteins spread across chromatin, and (iii) what does HP1 assembly do to chromatin structure? We will use a combination of quantitative biochemical methods and cutting edge electron cryo-microscopy approaches. We will also test key predictions of our models in vivo.

描述（由申请人提供）：异染色质的扩散对于遗传性沉默的基因组的大区域至关重要，因此对于在发育过程中产生和维持细胞身份至关重要。异染色质扩散丧失因侵入性乳腺癌的丧失而非法的基因激活，而异常异染色质扩散的非法基因沉默与髓样白血病密切相关。除基因沉默外，异染色质在重组和染色体分离中也起着至关重要的作用。在最保守的异染色质形式的核心是在组蛋白H3的赖氨酸9（H3K9me3）上形成的HP1蛋白和染色质甲基化的络合物（H3K9me3）。以下关键作用归因于HP1蛋白在异染色质函数中：（1）假设HP1-核体复合物可募集效应分子为H3K9me3染色质。自相矛盾的是，均可以募集这两种效应子，并限制进一步的异染色质扩散。这些相对活动之间的平衡被认为决定了组装异染色质的功能和稳定性。（2）假设HP1蛋白通过在多个核小体中寡聚来直接介导异染色质的扩散。（3）假设HP1蛋白将其凝结染色质，从而直接减少DNA对转录机械的访问。尽管这些特性对异染色质的体内功能具有中心性，但HP1如何完成这些角色的分子基础知之甚少。我们已经做出了新的发现，即SWI6是主要的pombe HP1同工型，它以自动抑制状态转换为散布能力的状态，其方式取决于对H3K9me3的识别以及核小体的其他特征。我们将基于这些和其他结果，以解决S. Pombe模型系统中的以下问题：（i）HP1蛋白如何与不同效应子相互作用，（iii）为什么不同的HP1同工型具有不同的功能，（iii）HP1蛋白如何在染色质中散布在染色质中，以及HP1组件对HP1组件有什么作用，HP1组件对铬蛋白结构有何作用？我们将结合定量生化方法和尖端电子冷冻微镜方法。我们还将测试体内模型的关键预测。