Bell G I, Stempien M M, Fong N M, Rall L B
Nucleic Acids Res. 1986 Oct 24;14(20):7873-82. doi: 10.1093/nar/14.20.7873.
Complementary DNAs encoding mouse liver insulin-like growth factor I (IGF-I) have been isolated and sequenced. Alternative RNA splicing results in the synthesis of two types of mouse IGF-I precursor that differ in the size and sequence of the COOH-terminal peptide. The sequences of the signal peptides, IGF-I moieties and the first 16 amino acids of the COOH-terminal peptides or E-domains of the two precursors are identical. The sequence difference results from the presence in preproIGF-IB mRNA of a 52 base insertion which introduces a 17 amino acid segment into the COOH-terminal peptide of preproIGF-IB and also causes a shift in the reading frame of the mRNA. As a consequence of this insertion, the COOH-terminal 19 and 25 amino acids of mouse preproIGF-IA and -IB, respectively, are different. The sequences of mouse and human preproIGF-IA are highly conserved and possess 94% identity. In contrast, the sequences of mouse and human preproIGF-IB are quite different in the region of the COOH-terminal peptide. A comparison of the sequences of mouse and human preproIGF-IB mRNA indicates that they are generated by different molecular mechanisms.
已分离并测序了编码小鼠肝脏胰岛素样生长因子I（IGF-I）的互补DNA。RNA的可变剪接导致合成两种类型的小鼠IGF-I前体，它们在COOH末端肽的大小和序列上有所不同。两种前体的信号肽、IGF-I部分以及COOH末端肽或E结构域的前16个氨基酸的序列是相同的。序列差异是由于preproIGF-IB mRNA中存在一个52个碱基的插入片段，该片段将一个17个氨基酸的片段引入preproIGF-IB的COOH末端肽中，同时也导致mRNA阅读框的移位。由于这种插入，小鼠preproIGF-IA和-IB的COOH末端分别有19和25个氨基酸不同。小鼠和人preproIGF-IA的序列高度保守，具有94%的同一性。相比之下，小鼠和人preproIGF-IB在COOH末端肽区域的序列差异很大。小鼠和人preproIGF-IB mRNA序列的比较表明，它们是由不同的分子机制产生的。
