Hampson R K, Rottman F M
Proc Natl Acad Sci U S A. 1987 May;84(9):2673-7. doi: 10.1073/pnas.84.9.2673.
We have detected a variant species of bovine growth hormone mRNA in bovine pituitary tissue and in a stably transfected bovine growth hormone-producing cell line. Analysis of this variant mRNA indicated that the last intervening sequence (intron D) had not been removed by splicing. Inspection of the sequence of intron D reveals an open reading frame through the entire intron, with a termination codon encountered 50 nucleotides into the fifth exon, which is shifted from the normal reading frame in this variant mRNA. If translated, this variant mRNA would encode a growth hormone-related polypeptide having 125 amino-terminal amino acids identical to wild-type growth hormone, followed by 108 carboxyl-terminal amino acids encoded by the 274 bases of intron D along with the first 50 nucleotides of exon 5. This variant polypeptide would be 42 amino acids longer than wild-type bovine growth hormone or approximately 5000 greater in molecular weight. The intron D-containing variant of bovine growth hormone mRNA was demonstrated to exist on polysomes, suggesting that this mRNA species is translated into a polypeptide. Cytosolic mRNA species containing any of the other three introns of the bovine growth hormone gene were not detectable.
我们在牛垂体组织和一个稳定转染的产牛生长激素细胞系中检测到了牛生长激素mRNA的一种变异体。对这种变异mRNA的分析表明，最后一个内含子序列（内含子D）未通过剪接去除。对内含子D序列的检查揭示了一个贯穿整个内含子的开放阅读框，在第五外显子中50个核苷酸处遇到一个终止密码子，该终止密码子在这种变异mRNA中与正常阅读框发生了移位。如果进行翻译，这种变异mRNA将编码一种与生长激素相关的多肽，其125个氨基末端氨基酸与野生型生长激素相同，随后是由内含子D的274个碱基以及外显子5的前50个核苷酸编码的108个羧基末端氨基酸。这种变异多肽比野生型牛生长激素长42个氨基酸，分子量大约大5000。含有内含子D的牛生长激素mRNA变异体被证明存在于多核糖体上，这表明这种mRNA可以被翻译成一种多肽。未检测到含有牛生长激素基因其他三个内含子中任何一个的胞质mRNA。
