Amara S G, David D N, Rosenfeld M G, Roos B A, Evans R M
Proc Natl Acad Sci U S A. 1980 Aug;77(8):4444-8. doi: 10.1073/pnas.77.8.4444.
A chimeric plasmic containing cDNA complementary to rat calcitonin mRNA has been constructed. Partial sequence analysis shows that the insert contains a nucleotide sequence encoding the complete amino acid sequence of calcitonin. Two basic amino acids precede and three basic amino acids follow the hormone sequence, suggesting that calcitonin is generated by the proteolytic cleavage of a larger precursor in a manner analogous to that of other small polypeptide hormones. The COOH-terminal proline, known to be amidated in the secreted hormone, is followed by a glycine in the precursor. The cloned calcitonin DNA was used to characterize the expression of calcitonin mRNA. Cytoplasmic mRNAs from calcitonin-producing rat medullary thyroid carcinoma lines and from normal rat thyroid glands contain a single species, 1050 nucleotides long, whch hybridizes to the cloned calcitonin cDNA. The concentration of calcitonin mRNA sequences is greater in those tumors that produce larger amounts of immunoreactive calcitonin. RNAs from other endocrine tissues, including anterior and neurointermediate lobes of rat pituitary, contain no detectable calcitonin mRNA.
已构建出一种嵌合质粒，其含有与大鼠降钙素mRNA互补的cDNA。部分序列分析表明，插入片段包含一个编码降钙素完整氨基酸序列的核苷酸序列。在激素序列之前有两个碱性氨基酸，之后有三个碱性氨基酸，这表明降钙素是以类似于其他小多肽激素的方式通过较大前体的蛋白水解切割产生的。已知在分泌的激素中羧基末端脯氨酸会被酰胺化，在前体中该脯氨酸之后是一个甘氨酸。克隆的降钙素DNA被用于表征降钙素mRNA的表达。来自产生降钙素的大鼠甲状腺髓样癌系和正常大鼠甲状腺的细胞质mRNA包含一种单一类型，长度为1050个核苷酸，其与克隆的降钙素cDNA杂交。在产生大量免疫反应性降钙素的那些肿瘤中，降钙素mRNA序列的浓度更高。来自其他内分泌组织的RNA，包括大鼠垂体的前叶和神经中间叶，未检测到降钙素mRNA。
