Single base mutation in the pro alpha 2(I) collagen gene that causes efficient splicing of RNA from exon 27 to exon 29 and synthesis of a shortened but in-frame pro alpha 2(I) chain.
Single base mutation in the pro alpha 2(I) collagen gene that causes efficient splicing of RNA from exon 27 to exon 29 and synthesis of a shortened but in-frame pro alpha 2(I) chain.
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Pro α 2(I) 胶原蛋白基因中的单碱基突变导致 RNA 从外显子 27 到外显子 29 的有效剪接，并合成缩短但符合读框的 Pro α 2(I) 链。
DOI：
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发表时间：
1988
影响因子：
11.1
通讯作者：
D. Prockop
中科院分区：
文献类型：
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作者：
G. Tromp;D. Prockop
先前的观察表明，成骨不全症的致命变异体具有两个 I 型原胶原前 α2(I) 链改变的等位基因。一种突变产生了无功能的等位基因，因为该等位基因合成了 mRNA，但未检测到原 α2(I) 链的合成。另一个等位基因的突变引起缩短的 pro α 2(I) 链的合成，该链缺乏外显子 28 编码的大部分或全部 18 个氨基酸。从先证者的 DNA 中制备 pro α 2(I) 基因的亚克隆，并确定了从插入序列 26 的最后 30 bp 延伸到插入序列的前 26 bp 的 582 碱基对 (bp) 区域的 DNA 序列。 29.来自六个独立亚克隆的数据表明，所有亚克隆都与先前分离的前α2(I)基因正常克隆具有相同的序列，除了四个亚克隆在插入序列27的3'末端具有单碱基突变。该突变是鸟嘌呤取代腺嘌呤，将RNA 3'剪接位点的通用共有序列从-AG-改变为-GG-。 S1核酸酶实验表明，先证者成纤维细胞中大约一半的pro alpha 2(I) mRNA被异常剪接，并且异常pro alpha 2(I) mRNA的主要种类从外显子27的最后一个密码子到外显子29的第一个密码子完全剪接。该突变在哺乳动物系统的RNA剪接突变中显然是唯一的，它产生了编码符合读框的缩短的多肽链序列，用于蛋白质的亚基组装，并有助于致命的表型。
Previous observations demonstrated that a lethal variant of osteogenesis imperfecta had two altered alleles for pro alpha 2(I) chains of type I procollagen. One mutation produced a nonfunctioning allele in that there was synthesis of mRNA but no detectable synthesis of pro alpha 2(I) chains from the allele. The mutation in the other allele caused synthesis of shortened pro alpha 2(I) chains that lacked most or all of the 18 amino acids encoded by exon 28. Subclones of the pro alpha 2(I) gene were prepared from the proband's DNA and the DNA sequence was determined for a 582-base-pair (bp) region that extended from the last 30 bp of intervening sequence 26 to the first 26 bp of intervening sequence 29. Data from six independent subclones demonstrated that all had the same sequence as a previously isolated normal clone for the pro alpha 2(I) gene except that four subclones had a single base mutation at the 3' end of intervening sequence 27. The mutation was a substitution of guanine for adenine that changed the universal consensus sequence for the 3' splicing site of RNA from -AG- to -GG-. S1 nuclease experiments demonstrated that about half the pro alpha 2(I) mRNA in the proband's fibroblasts was abnormally spliced and that the major species of abnormal pro alpha 2(I) mRNA was completely spliced from the last codon of exon 27 to the first codon of exon 29. The mutation is apparently unique among RNA splicing mutations of mammalian systems in producing a shortened polypeptide chain that is in-frame in terms of coding sequences, that is used in the subunit assembly of a protein, and that contributes to a lethal phenotype.