CONTROL OF ALPHA 2 (1) COLLAGEN PRODUCTION IN CARTILAGE

描述：(改编自调查人员摘要)胶原蛋白，最 高等真核生物结缔组织中丰富的蛋白质 在许多组织和器官中起着重要的结构作用。胶原蛋白 生产受到严格的发育控制，每种细胞类型 只产生全部胶原蛋白的一个子集。这间牢房- 胶原蛋白合成的类型特异性在很大程度上决定了 组织的结构和物理性质。最好的之一 发育调节的胶原蛋白产生的典型例子 是间充质细胞分化为透明软骨。少校 软骨形成前间质中的胶原为I型；作为间质 细胞分化为软骨细胞，停止产生I型 胶原蛋白和启动软骨特异性胶原蛋白的合成，尽管 肥大的软骨细胞中I型胶原的合成在 软骨-骨性交界处。此外，有证据表明， I型胶原基因表达的异常再启动 骨关节炎关节软骨。相对较少的是 关于调节这些变化的分子机制的信息 正常和异常胶原产生的转变，尽管它们 对骨骼发育的重要性。一种不同寻常的机制是 发现能阻止α2(I)胶原亚单位的合成 小鸡软骨。之前确定的(上游)启动子 α2(I)胶原基因在软骨中被抑制，但内部 促进剂被激活，导致产生一种替代 不编码α2(I)胶原蛋白的转录本。这一变化在 启动子的使用有效地阻止了α2(I)胶原的合成 也可能导致产生一种以前未知的 非胶原蛋白。这份续签申请建议：1) 继续定义顺式元件和转录因子 介导软骨细胞特异性激活骨形成蛋白内部启动子 鸡α2(I)胶原蛋白基因。涉及的四个域 已经确定了软骨细胞特异的转录活性； 这些结构域中的顺式元件将被表征并转录 将确定与其交互的因素；2)定义配置项 介导软骨细胞特异性的元件和转录因子 α2(I)胶原基因上游启动子的抑制；3) 确定被废止的替代物生产的影响 预测蛋白的转录本和异位表达；4)纯化 并对这种小的RNA结合蛋白进行了表征，这种蛋白似乎是 α2(I)胶原蛋白选择性转录本的主要产物 吉恩。这种多方面的实验方法旨在进一步推动我们的 对发育相关的分子机制的理解 软骨形成过程中α2(I)胶原蛋白的调节产生 正常骨骼发育的重要过程，以及 在骨关节炎中的异常表达。

DESCRIPTION: (Adapted from investigator's abstract) Collagens, the most abundant proteins in connective tissues of higher eukaryotes, play important structural roles in many tissues and organs. Collagen production is under strict developmental control, and each cell type produces only a subset of the total repertoire of collagens. This cell- type specificity of collagen synthesis determines, to a large extent, the architecture and physical properties of tissues. One of the best characterized examples of developmentally-regulated collagen production is the differentiation of mesenchyme into hyaline cartilage. The major collagen in prechondrogenic mesenchyme is type I; as the mesenchymal cells differentiate into chondrocytes, they stop producing type I collagen and initiate synthesis of cartilage-specific collagens, although type I collagen synthesis is reinitiated in hypertrophic chondrocytes at the chondro-osseous junction. In addition, there is evidence for abnormal reinitiation of type I collagen gene expression in osteoarthritic articular cartilage. There is relatively little information regarding the molecular mechanisms that mediate these transitions in normal and abnormal collagen production, despite their importance for skeletal development. An unusual mechanism has been discovered that prevents synthesis of the alpha2(I) collagen subunit in chick cartilage. The previously identified (upstream) promoter of the alpha2(I) collagen gene is repressed in cartilage, but an internal promoter is activated, resulting in production of an alternative transcript that does not encode alpha2(I) collagen. This change in promoter utilization effectively prevents alpha2(I) collagen synthesis in cartilage and may also result in production of a previously unknown noncollagenous protein. This renewal application proposes to: 1) continue to define the cis elements and transcription factors that mediate chondrocyte-specific activation of the internal promoter of the chick alpha2(I) collagen gene. Four domains that are involved in chondrocyte-specific transcriptional activity have been identified; the cis elements in these domains will be characterized and the transcription factors that interact with them will be identified; 2) define the cis elements and transcription factors the mediate chondrocyte-specific repression of the upstream promoter of the alpha2(I) collagen gene; 3) determine the effects of abrogated production of the alternative transcript and ectopic expression of the predicted protein; and 4) purify and characterize the small RNA-binding protein that appears to be the major product of the alternative transcript of the alpha2(I) collagen gene. This multifaceted experimental approach is intended to further our understanding of the molecular mechanisms underlying the developmentally regulated production of alpha2(I) collagen during chondrogenesis, an important process for normal skeletal development, as well as the abnormal expression in osteoarthritis.