TYPE III GENE EXPRESSION IN CARTILAGE

III型胶原蛋白存在于大多数结缔组织中，但没有发现 在透明软骨中。 然而，一种独特的III型胶原相关RNA 在鸡的软骨中被检测到 这3800个碱基的RNA要小得多 比真正的5700个核苷酸的III型胶原mRNA， 太小而不能编码正常的III型胶原亚单位。 外显子21-52 这种RNA与真正的III型胶原蛋白相似或相同 mRNA，但外显子1-16似乎从RNA的5'端缺失， 这表明，可能有一个替代的转录起始位点， III型胶原基因，其优先用于软骨。 软骨中缺乏III型胶原蛋白可能是由于 改变RNA结构 提出了实验来确定 III型胶原相关RNA的结构，并将其与 真正的III型胶原mRNA。 鸡III型的5'端 还将分离胶原蛋白基因，并且启动子和任何 以前未描述的外显子将通过比较 外显子/内含子组织与序列的真实类型 III型胶原mRNA和III型胶原相关RNA。 这些 实验将表明是否在结构上的差异， 软骨RNA是由于使用替代启动子，替代RNA 处理事件或两者。 他们还将定义任何开放的阅读 RNA中的框架，从而表明RNA是否可能编码一个 蛋白质（非胶原蛋白或III型胶原蛋白的改变形式 胶原蛋白）。 顺式作用序列和反式作用因子 对于III型胶原的启动子的功能是重要的 将鉴定适当组织中的基因。 最后 软骨III型胶原蛋白相关RNA的功能将是 测定 如果基于序列和亚细胞分布数据， III型胶原相关RNA似乎编码一种蛋白质， 将被分离并鉴定。 这些实验将提供 增加对防止生产的分子机制的了解 软骨中的III型胶原蛋白，并将提供更广泛的 III型胶原基因结构分析及其在人乳腺癌中的应用 比以往任何时候都要规范。 这些关于III型糖尿病的研究 胶原蛋白基因表达，以及正在进行的研究α 2（I） 胶原蛋白基因表达，暗示了一种有趣的可能性， 可能是胶原基因的一个子集，编码mRNA的替代形式 在软骨中。

Type III collagen is found in most connective tissues, but is not found in hyaline cartilage. However, a unique type III collagen-related RNA has been detected in chick cartilage. This 3800 base RNA is much smaller than the authentic 5700 nucleotide type III collagen mRNA, and is in fact too small to encode a normal type III collagen subunit. Exons 21-52 of this RNA are similar or identical to the authentic type III collagen mRNA, but exons 1-16 appear to be missing from the 5' end of the RNA, suggesting that there may be an alternative transcription start site in the type III collagen gene which is used preferentially in cartilage. The absence of type III collagen in cartilage is presumably due to the altered RNA structure. Experiments are proposed to determine the structure of the type III collagen-related RNA and compare it with the authentic type III collagen mRNA. The 5' end of the chick type III collagen gene will also be isolated, and the promoter(s) and any previously undescribed exons will be identified by comparison of the exon/intron organization with the sequences of both the authentic type III collagen mRNA and the type III collagen-related RNA. These experiments will indicate whether the structural differences in the cartilage RNA are due to use of an alternative promoter, alternative RNA processing events, or both. They will also define any open reading frames in the RNA, thus indicating whether the RNA is likely to encode a protein (either a non-collagen protein or an altered form of type III collagen). The cis-acting sequences and trans-acting factors that are important for the function of the promoter(s) of the type III collagen gene in the appropriate tissues will be identified. Finally, the function of the cartilage type III collagen-related RNA will be determined. If, based on sequence and subcellular distribution data, the type III collagen-related RNA appears to encode a protein, the protein will be isolated and characterized. These experiments will provide increased understanding of the molecular mechanisms preventing production of type III collagen in cartilage, and will provide more extensive analysis of the structure of the type III collagen gene and its regulation than has heretofore been available. These studies on type III collagen gene expression, together with ongoing studies of alpha2(I) collagen gene expression, suggest the intriguing possibility that there may be a subset of collagen genes that encode alternative forms of mRNA in cartilage.