Amara S G, Evans R M, Rosenfeld M G
Mol Cell Biol. 1984 Oct;4(10):2151-60. doi: 10.1128/mcb.4.10.2151-2160.1984.
Different 3' coding exons in the rat calcitonin gene are used to generate distinct mRNAs encoding either the hormone calcitonin in thyroidal C-cells or a new neuropeptide referred to as calcitonin gene-related peptide in neuronal tissue, indicating the RNA processing regulation is one strategy used in tissue-specific regulation of gene expression in the brain. Although the two mRNAs use the same transcriptional initiation site and have identical 5' terminal sequences, their 3' termini are distinct. The polyadenylation sites for calcitonin and calcitonin gene-related peptide mRNAs are located at the end of the exons 4 and 6, respectively. Termination of transcription after the calcitonin exon does not dictate the production of calcitonin mRNA, because transcription proceeds through both calcitonin and calcitonin gene-related peptide exons irrespective of which mRNA is ultimately produced. In isolated nuclei, both polyadenylation sites appear to be utilized; however, the proximal (calcitonin) site is preferentially used in nuclei from tissues producing calcitonin mRNA. These data suggest that the mechanism dictating production of each mRNA involves the selective use of alternative polyadenylation sites.
大鼠降钙素基因中不同的3'编码外显子用于生成不同的mRNA，这些mRNA在甲状腺C细胞中编码激素降钙素，而在神经组织中编码一种称为降钙素基因相关肽的新神经肽，这表明RNA加工调控是大脑中基因表达的组织特异性调控所采用的一种策略。尽管这两种mRNA使用相同的转录起始位点且具有相同的'5末端序列，但它们的3'末端是不同的。降钙素和降钙素基因相关肽mRNA的聚腺苷酸化位点分别位于外显子4和6的末端。降钙素外显子后的转录终止并不决定降钙素mRNA的产生，因为无论最终产生哪种mRNA，转录都会通过降钙素和降钙素基因相关肽外显子进行。在分离的细胞核中，两个聚腺苷酸化位点似乎都被利用；然而，近端（降钙素）位点在产生降钙素mRNA的组织的细胞核中被优先使用。这些数据表明，决定每种mRNA产生的机制涉及对替代聚腺苷酸化位点的选择性使用。
