SWI/SNF-related complex in osteoblast differentiation

描述(申请人提供)：哺乳动物SWI/SNF相关复合体是组织特异性基因表达所必需的。这些复合体的成分在进化上是保守的，首先在酵母中被发现，它们是基因表达变化所必需的，基因表达的变化介导了交配型转换(SWI)和在没有葡萄糖的情况下切换到蔗糖利用的能力(蔗糖-非发酵剂)。这些复合体包含依赖于DNA的ATPase活性，该活性增强了核小体重塑功能，进而允许转录因子访问启动子位置。酵母复合体一直是广泛遗传分析的目标，人们已经做了大量的工作来研究酵母和哺乳动物复合体重塑核小体的机制，但令人惊讶的是，人们对该复合体及其单个成分在哺乳动物细胞分化中的生物学作用知之甚少。已知的是，取消该复合体的ATPase活性会阻止一系列组织类型的正常分化功能。ATPase是复合体的分子马达，对其功能当然是必不可少的，但复合体包含七个或更多其他成分，据信这些成分可以调节复合体对特定信号的反应，特别是对激素的反应。关于这些可调节的、非催化的亚基的生物学作用，现有的信息非常有限。阐明它们的作用将使人们对这些复合体如何在精确调控的代谢过程中实现功能的特异性提供亟需的见解。因此，该项目建议开发分化模型，在该模型中，特定的复杂成分将在单个生物系统中单独耗尽。由此产生的表型将表明单个亚基的生物学作用。分化模型将在成骨前细胞系中开发，因为这些细胞对多种细胞外信号做出反应，并具有高度调节和顺序的分化程序，该程序具有良好的特性，并包括细胞周期调节。拟议的系统将提供重要的临床数据，与广泛的公共卫生问题有关，如骨质疏松症和炎症性疾病，以及癌症。

DESCRIPTION (provided by applicant): Mammalian SWI/SNF-related complexes are required for tissue specific gene expression. The components of these complexes are evolutionarily conserved, and were first identified in yeast, where they are required for the changes in gene expression that mediate the mating type switch (SWI) and the ability to switch to sucrose utilization in the absence of glucose (Sucrose-Non-Fermentors). The complexes contain a DNA-dependent ATPase activity that powers a nucleosome remodeling function, which in turn allows transcription factor access to promoter sites. The yeast complexes have been the target of extensive genetic analysis, and considerable work has been done to address the mechanisms of nucleosome remodeling by yeast and mammalian complexes, but surprisingly little is known about the biological role of the complex and its individual components in the differentiation of mammalian cells. What is known is that abrogation of the ATPase activity of the complex blocks normal differentiation function in a range of tissue types. The ATPase is the molecular motor of the complex and is, of course essential to its function, but the complexes contain seven or more other components that are believed to modulate the activity of the complex in response to specific signals, particularly in response to hormones. Very limited information is available on the biological role of these modulatory, non-catalytic, subunits. Elucidation of their roles would give much-needed insight into how the complexes achieve specificity of function in precisely regulated metabolic processes. This project therefore proposes the development of differentiation models in which specific complex components will be depleted individually within a single biological system. The resulting phenotypes will indicate the biological roles of the individual subunits. The differentiation models will be developed in a pre-osteoblast line because these cells are responsive to multiple extracellular signals and have a highly regulated and sequential differentiation program that is well-characterized and includes cell cycle regulation. The proposed systems will provide important clinical data, relevant to broad public health problems, such as osteoporosis and inflammatory diseases, as well as to cancer.