SWI/SNF-related complex in osteoblast differentiation

描述（由申请人提供）：组织特异性基因表达需要哺乳动物SWI/SNF相关复合物。这些复合物的组分在进化上是保守的，并且首先在酵母中被鉴定，其中它们是介导交配型转换（SWI）的基因表达变化和在不存在葡萄糖的情况下转换为蔗糖利用的能力所必需的（蔗糖非发酵剂）。该复合物含有DNA依赖性ATP酶活性，其为核小体重塑功能提供动力，从而允许转录因子进入启动子位点。酵母复合物一直是广泛的遗传分析的目标，并且已经做了大量的工作来解决酵母和哺乳动物复合物的核小体重塑机制，但令人惊讶的是，对复合物及其单个组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，复合物的ATP酶活性的消除阻断了一系列组织类型中的正常分化功能。ATP酶是复合物的分子马达，当然对其功能至关重要，但复合物含有七种或更多种其他组分，据信这些组分响应特定信号，特别是响应激素，调节复合物的活性。关于这些调节性、非催化性亚基的生物学作用的信息非常有限。阐明它们的作用将使人们对复合物如何在精确调节的代谢过程中实现功能特异性有更深入的了解。因此，该项目提出了分化模型的发展，其中特定的复杂成分将在一个单一的生物系统中单独耗尽。由此产生的表型将指示各个亚基的生物学作用。分化模型将在前成骨细胞系中开发，因为这些细胞对多种细胞外信号有反应，并且具有高度调节和顺序的分化程序，该程序被充分表征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.