Tissue Specific Function of Basement Membrane and Heterogeneity in Matrix Molecules

我们分离了编码人和兔α4(IV)胶原链的重叠的cDNA。克隆的鉴定和测序证实了人和兔α4(IV)胶原链的一级结构。该链的氨基酸序列与α2(IV)胶原链的氨基酸序列同源。通过原位杂交将该基因定位于染色体2q35-37.1。有趣的是，编码α4(IV)胶原链的mRNA的大小明显大于编码IV型胶原链的其他四个mRNAs。比较这五个α(IV)链的序列，发现该基因有两个亚类：α1、α3和α5链基因以及α2和α4链基因。通过这些分析，我们预测还有一个α(IV)链属于α2(IV)和α4(IV)链的基因。在低严格性条件下，我们成功地分离到编码另一条α(IV)胶原链的新基因。我们将他的新链命名为字母6(IV)链。有趣的是，该基因的染色体位置被分配到染色体Xq22，这与α5(IV)胶原链基因的位置相同。我们进一步分离了编码α6(IV)链和α5(IV)链的多个基因片段。对基因片段的精确分析表明，这两个基因位于相同的片段上，但排列在相反的方向上，共享基因中心的双向启动子。此外，在alpha6(IV)基因的真实启动子下游约有1000个碱基的另一个启动子。

We isolated overlapping cDNAs encoding the human and rabbit alpha4(IV) collagen chains. Charcterization and sequencing of the clones demonstrated the primary structure of the human and rabbit alpha4(IV) collagen chains. The amino acid sequence of the chain is homologous to that of the alpha2(IV) collagen chain. Chromosomal location of the gene was assigned to chromosome 2q35-37.1 by in situ hybridization. Interestingly, the size of the mRNA coding for the alpha4(IV) collagen chain is significantly larger than the other four mRNAs for type IV collagen chains. Comparison of the sequences for these five alpha(IV) chains revealed that there are two subclasses of the gene ; the genes for alpha1, alpha3, and alpha5 chains and genes for alpha2 and alpha4 chains. By these analyzes we predicted that there was one more alpha(IV) chain that belonged to the genes for the alpha2(IV) and alpha4(IV) chains. Using low stringency conditions we successfully isolated a novel cDNA encoding yet another alpha(IV) collagen chain. We designated his new chain as alpha6(IV) chain. Of interest was that the chromosomal location of the gene was assigned to chromosome Xq22, which is the same location as the gene for alpha5(IV) collagen chain. We furtheer isolated several fragments of the gene coding for the alpha6(IV) chain and also the alpha5(IV) chain at the same time. Precise analysis of the fragment of the genes revealed that the genes were located on the same fragement but aligned onto the opposite directions sharing bidirectional promoter in the center of the genes. Further, there was an alternativepromoter approximately 1000 bases downstream of the authentic promoter for the alpha6(IV) gene.