A 5' SPLICE-SITE MUTATION AFFECTING THE PRE-MESSENGER-RNA SPLICING OF 2 UPSTREAM EXONS IN THE COLLAGEN COL1A1 GENE - EXON-8 SKIPPING AND ALTERED DEFINITION OF EXON-7 GENERATES TRUNCATED PRO-ALPHA-1(I) CHAINS WITH A NONCOLLAGENOUS INSERTION DESTABILIZING THE TRIPLE-HELIX
A 5' SPLICE-SITE MUTATION AFFECTING THE PRE-MESSENGER-RNA SPLICING OF 2 UPSTREAM EXONS IN THE COLLAGEN COL1A1 GENE - EXON-8 SKIPPING AND ALTERED DEFINITION OF EXON-7 GENERATES TRUNCATED PRO-ALPHA-1(I) CHAINS WITH A NONCOLLAGENOUS INSERTION DESTABILIZING THE TRIPLE-HELIX
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DOI：
10.1042/bj3020729
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发表时间：
1994-09-15
影响因子：
4.1
通讯作者：
COLE, WG
中科院分区：
文献类型：
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作者：
BATEMAN, JF;CHAN, D;COLE, WG
1例IV型成骨不全患者在I型前胶原蛋白（COLIA1）原α 1(I)链基因剪接供体位点+5位置的8号内含子中出现G到A点的杂合突变。剪接供体位点突变不仅导致上游外显子8的跳跃，而且出乎意料地具有激活下一个上游内含子内含子7的隐剪接位点的二次效应，导致外显子7的3'极限重新定义。这些前mRNA剪接畸变导致成熟mRNA的外显子8序列缺失，内含子7序列包含96 bp。由于突变等位基因产物的错误剪接导致正确密码子阅读框的维持，因此产生的pro α 1(I)链在重复的Gly-Xaa-Yaa胶原序列基序中包含一个短的非胶原32个氨基酸序列插入。在蛋白质水平上，突变的α 1(I)链通过胃蛋白酶的消化被发现，胃蛋白酶在蛋白酶敏感的非胶原插入处切割突变的前胶原，产生截断的α 1(I)。这种蛋白酶的敏感性证明了插入引起的螺旋结构的结构扭曲。在抗坏血酸的长期培养中，刺激成熟交联胶原基质的形成，在组织中，没有发现突变链的证据，这表明在基质形成过程中，突变链不能稳定地结合到基质中，并被蛋白水解降解。
A heterozygous de novo G to A point mutation in intron 8 at the +5 position of the splice donor site of the gene for the pro alpha 1(I) chain of type I procollagen, COLIA1, was defined in a patient with type IV osteogenesis imperfecta. The splice donor site mutation resulted not only in the skipping of the upstream exon 8 but also unexpectedly had the secondary effect of activating a cryptic splice site in the next upstream intron, intron 7, leading to re-definition of the 3' limit of exon 7. These pre-mRNA splicing aberrations cause the deletion of exon 8 sequences from the mature mRNA and the inclusion of 96 bp of intron 7 sequence. Since the mis-splicing of the mutant allele product resulted in the maintenance of the correct codon reading frame, the resultant pro alpha 1(I) chain contained a short non-collagenous 32-amino-acid sequence insertion within the repetitive Gly-Xaa-Yaa collagen sequence motif. At the protein level, the mutant alpha 1(I) chain was revealed by digestion with pepsin, which cleaved the mutant procollagen within the protease-sensitive noncollagenous insertion, producing a truncated alpha 1(I). This protease sensitivity demonstrated the structural distortion to the helical structure caused by the insertion. In long-term culture with ascorbic acid, which stimulates the formation of a mature crosslinked collagen matrix, and in tissues, there was no evidence of the mutant chain, suggesting that during matrix formation the mutant chain was unable to be stably incorporated into the matrix and was degraded proteolytically.