Nuclear & Chromatin Packaging of Mammalian X Chromosome

描述(申请人提供)：哺乳动物的X染色体通过形成兼性异染色质，构成基因组调节的重要生物学和临床模型，异染色质是正常发育的中心现象，在癌症中被废除。正如我们早先假设的那样，稳定的XIST RNA的积累在结构上与女性的一条X染色体相关，并启动了一个复杂的染色体重塑过程。现在，一个中心问题变成了：XIST RNA如何“绘制”它的亲本染色体，并导致整个染色体的全面凝聚和永久抑制？我们的方法允许分子、生化和结构分析彼此直接相关，并将与基因组序列组织的生物信息学相结合。研究包括肿瘤抑制因子BRCA1的作用，最近的发现与XIST RNA有关，以及维持剂量补偿。其他关键问题涉及生化和结构变化与转录抑制的相互关系，XIST何时在正常胚胎环境中表达，以及何时发育或染色体环境受到操纵。人类基因组序列分析将有可能揭示与染色体结构和XIST RNA结合有关的“垃圾”DNA中的序列。这项研究的意义从阐明发育基因调控和染色体结构的基本机制，到检验具有直接临床意义的创新假设和方法。

DESCRIPTION (provided by applicant): The mammalian X chromosome constitutes a vital biological and clinical model for genome regulation through formation of facultative heterochromatin, a phenomenon central to normal development and abrogated in cancer. As we earlier hypothesized, an accumulation of stable XIST RNA structurally associates with one X chromosome in females and initiates a complex process of chromosome remodeling. A central issue now becomes: how does XIST RNA "paint" its parent chromosome and lead to the sweeping condensation and permanent repression of the whole chromosome? Our approach allows molecular, biochemical and structural analyses in direct relation to one another, and will be coupled with bioinformatics of genomic sequence organization. Studies include the role of the tumor suppressor, BRCA1, which recent findings link to XIST RNA and maintenance of dosage compensation. Other key questions address the interrelationship of biochemical and structural changes with transcriptional repression, when XIST is expressed in normal embryonic context, and when the developmental or chromosomal context is manipulated. Human genome sequence analysis will be pursued with potential to reveal sequences in "junk" DNA involved in chromosome architecture and XIST RNA binding. The significance of this research extends from elucidating fundamental mechanisms of developmental gene regulation and chromosome structure, to testing innovative hypotheses and approaches with direct clinical implications.