Role of Heterochromatin protein 1 Beta in Genome Maintenance and Oncogenesis

异染色质蛋白 1 Beta 在基因组维护和肿瘤发生中的作用

• 批准号: 8657357
• 负责人: Tej K Pandita
• 金额: $ 30.31万
• 依托单位: METHODIST HOSPITAL RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-16 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8657357
• 关键词: Acetylation; Appearance; Applications Grants; Binding; Biochemical; C-terminal; Cancer Patient; Cell Communication; Cell Survival; Cell physiology; Cells; Cessation of life; ChIP-on-chip; Chromatin; Chromatin Structure; Chromosomes, Human, Pair 1; Clinical; Co-Immunoprecipitations; Complement; Complex; DNA; DNA Damage; DNA Double Strand Break; DNA Repair; DNA-PKcs; Data; Development; Double Strand Break Repair; Embryo; Euchromatin; Eukaryota; Fibroblasts; Frequencies; Genes; Genome; Genomic Instability; Genomics; Goals; Heterochromatin; Histone H3; Histone H4; Histones; Human; Image; Individual; Investigation; Ionizing radiation; Kinetics; Knockout Mice; Lasers; Lesion; Link; Lysine; Maintenance; Mammalian Cell; Mammals; Mammary Gland Parenchyma; Maps; Mediating; Modification; Mus; N-terminal; NBS1 gene; Neoplastic Cell Transformation; Normal Cell; Normal tissue morphology; Oncogenic; Pathway interactions; Phenotype; Play; Post-Translational Protein Processing; Predisposition; Protein Isoforms; Proteins; Radiation Induced DNA Damage; Radiation Tolerance; Radiation therapy; Reporting; Research; Research Personnel; Role; Site; Tail; Testing; Time; Tissues; Tumor Tissue; Zinc Fingers; ataxia telangiectasia mutated protein; base; cell injury; cell killing; chromatin protein; expression vector; heterochromatin-specific nonhistone chromosomal protein HP-1; histone modification; improved; in vivo; insight; novel; novel strategies; nuclease; overexpression; prevent; public health relevance; repaired; response; tumor; tumorigenesis

The DNA damage response (DDR) mediates DNA double strand break (DSB) repair and protects cells from damage induced transformation or death. Cellular DNA is organized into protein DNA complexes (chromatin) in order to control DNA access by proteins and regulated DNA dependent functions. In eukaryotes, there are two major types of chromatin: heterochromatin (gene poor) and euchromatin (gene rich) that are distinguished by specific histone tail modifications and differences in nonhistone chromatin protein constituents. Among nonhistone chromatin proteins, heterochromatin protein 1 (HP1) is the best- studied example. In mammals, there are three HP1 isoforms (HP1a, HP1b and HP1g) all structurally characterized by two conserved domains separated by a hinge region: an N-terminal chromodomain (CD) and a C-terminal chromoshadow domain (CSD). We previously demonstrated that overexpression of HP1a or HP1b in human cells increases genomic instability and sensitivity to ionizing radiation (IR)-induced cell killing. Moreover, depletion of Cbx1 (mouse HP1b) in mouse cells increased genomic instability, spontaneous ATM (ataxia-telangiectasia mutated) autophosphorylation, reduced the frequency of IR-induced g-H2AX foci formation, increased IR-induced cell killing and oncogenic transformation. Recent studies by other investigators support our results indicating HP1b has both negative as well as positive effects on DNA DSB repair and suggest that the precise level of functional HP1b is a critical determinant to IR sensitivity. Since most mechanistic details as to how HP1 b interacts with repair associated proteins to modulate DNA DSB repair are unexplored, we will determine how different domains interact with chromatin/repair protein components to regulate DNA DSB repair. We hypothesize that the negative effect of HP1b is mediated through CD domain binding to H3K9me, since deletion of this domain can improve cell survival and the positive effect could be due to HP1b CSD interactions with acetylated histone H4K16 (H4K16ac) a unique histone modification that prevents higher order chromatin packing, which can impede protein access to DNA and with proteins involved in the DDR. Defective DNA damage repair is linked with oncogenic transformation and tumorigenesis, therefore, we will determine the impact of decreased Cbx1 on tumor development in (i) Cbx1+/- mice in the presence and absence of Atm and (ii) Cbx1 conditional knockout mice. These studies will define the mechanism by which HP1b regulates the cellular IR response and tumorigenesis. Our hypothesis-that the non-histone modifying factor HP1b regulates chromatin structure and, through interactions with DDR components, contributes to oncogenesis-is a novel idea requiring in depth studies. Further understanding about the mechanistic basis for biochemical differences between normal and tumor tissue chromatin structure will facilitate the development of new strategies for modifying IR response and improving clinical radiation therapy.

DNA损伤反应（DDR）介导DNA双链断裂（DSB）修复并保护细胞 由损伤引起的变形或死亡细胞DNA被组织成蛋白质DNA复合物 （染色质）以控制蛋白质对DNA的访问并调节DNA依赖性功能。在 在真核生物中，有两种主要类型的染色质：异染色质（基因贫乏）和常染色质（基因贫乏）。 丰富），其区别在于特定的组蛋白尾部修饰和非组蛋白染色质的差异 蛋白质成分在非组蛋白染色质蛋白中，异染色质蛋白1（HP 1）是最好的- 研究的例子。在哺乳动物中，存在三种HP 1同种型（HP 1a、HP 1b和HP 1g），其结构均为 其特征在于由铰链区分开的两个保守结构域：N-末端染色体结构域（CD） 和C-末端chromoshadow结构域（CSD）。我们以前证明过表达HP 1a 或HP 1b增加基因组不稳定性和对电离辐射（IR）诱导的细胞敏感性 杀人此外，小鼠细胞中Cbx 1（小鼠HP 1b）的缺失增加了基因组的不稳定性， 自发ATM（共济失调-毛细血管扩张突变）自身磷酸化，减少IR诱导的 g-H2 AX灶形成，增加IR诱导的细胞杀伤和致癌转化。最近的研究 其他研究人员支持我们的结果，表明HP 1b对DNA既有负面影响，也有正面影响 DSB修复，并表明功能性HP 1b的精确水平是IR敏感性的关键决定因素。 由于大多数关于HP 1 B如何与修复相关蛋白相互作用以调节DNA的机制细节 DSB修复尚未探索，我们将确定不同的结构域如何与染色质/修复蛋白相互作用 调节DNA DSB修复的组分。我们假设HP 1b的负作用是通过 通过CD结构域与H3 K9 me结合，因为该结构域的缺失可以改善细胞存活， 积极的影响可能是由于HP 1b CSD与乙酰化组蛋白H4 K16（H4 K16 ac）的相互作用， 组蛋白修饰，阻止高级染色质包装，这可能会阻碍蛋白质进入DNA 以及参与DDR的蛋白质。 DNA损伤修复缺陷与致癌转化和肿瘤发生有关，因此，我们 将确定Cbx 1减少对（i）Cbx 1 +/-小鼠中肿瘤发展的影响， Atm缺失和（ii）Cbx 1条件性敲除小鼠。这些研究将确定 HP 1b调节细胞IR反应和肿瘤发生。我们的假设-非组蛋白修饰 因子HP 1b调节染色质结构，并通过与DDR组分的相互作用， 肿瘤发生是一个新的概念，需要深入研究。对机械基础的再认识 对于正常和肿瘤组织之间的生化差异，染色质结构将有助于 开发新的策略来改善IR反应和改善临床放射治疗。