Human fibronectin: cell specific alternative mRNA splicing generates polypeptide chains differing in the number of internal repeats.
Human fibronectin: cell specific alternative mRNA splicing generates polypeptide chains differing in the number of internal repeats.
复制标题
人纤连蛋白：细胞特异性选择性 mRNA 剪接产生内部重复数量不同的多肽链。
作者：
A. Kornblihtt;K. Vibe;F. Baralle
测定了5个独立cDNA克隆的核苷酸序列，覆盖了人纤维连接蛋白（FN） mRNA多A加成位点的4843个核苷酸。推导出的氨基酸序列（1383个残基）覆盖了60%的人类FN的cooh末端，跨越了c端、纤维蛋白、肝素和细胞结合域，并显示了每个亚基链中仅有的两个游离巯基的确切位置。我们最近报道了两种不同的FN mRNA；其中一个包含额外的270个核苷酸插入（ED），该插入正好编码该蛋白的一个同源III型重复序列。这两种mrna是由一个共同前体的交替剪接产生的。cDNA/RNA杂交体的S1核酸酶图谱显示，这两种mrna的表达具有细胞特异性。肝脏只产生不含ED的mRNA，而肝癌细胞、乳腺肿瘤细胞和正常成纤维细胞同时产生这两种形式的mRNA。Schwarzbauer等人报道了在大鼠肝脏中产生三种不同FN mrna的另一个选择性剪接区域（16）。我们在这里提供了证据，证明在人类细胞中存在第四种mRNA，不同于在大鼠肝脏中描述的三种。
The nucleotide sequence of five independent cDNA clones, which cover 4843 nucleotides from the poly(A) addition site of human fibronectin (FN) mRNA was determined. The deduced amino acid sequence (1383 residues) covers the COOH-terminal 60% of human FN, spanning the C-terminus, fibrin-, heparin- and cell-binding domains, and shows the exact location of the only two free sulphydryl groups present in each subunit chain. We have recently reported two different FN mRNA species; one of them containing an additional 270 nucleotide insert (ED) that encodes exactly one of the homology type III repeats of the protein. The two mRNAs arise by alternative splicing of a common precursor. S1 nuclease mapping of cDNA/RNA hybrids shows that the expression of the two mRNAs is cell specific. Liver only produces the mRNA without the ED, whereas hepatoma cells, breast tumor cells and normal fibroblasts produce both forms of mRNA. Another area of alternative splicing generating three different FN mRNAs in rat liver has been reported by Schwarzbauer et al (16). We here provide evidence for the existence in human cells of a fourth mRNA species different from the three described in rat liver.