Narayan P, Liaw C W, Towle H C
Proc Natl Acad Sci U S A. 1984 Aug;81(15):4687-91. doi: 10.1073/pnas.81.15.4687.
Administration of thyroid hormone to the thyroidectomized rat results in a rapid and dramatic increase in the relative amount of hepatic mRNA coding for spot 14--a translational product with an approximate Mr of 17,500 and isoelectric point of 4.9. We have now isolated a cDNA clone containing sequences homologous to this thyroid hormone-responsive mRNA. Two distinct mRNA species that differed by 200 nucleotides in length were found to be capable of hybridizing to the cDNA probe. Both mRNA species were proportionally elevated in relative concentration in rats with increasing plasma levels of thyroid hormone. The earliest change in the levels of mature mRNA occurred at 20 minutes following thyroid hormone treatment of the thyroidectomized rat. Analysis of nuclear RNA revealed a single higher molecular weight species that was homologous to spot 14 mRNA. An increase in the nuclear level of this putative precursor occurred by 10 minutes following thyroid hormone administration, a time preceding the earliest change in mature mRNA. Thus, thyroid hormone appears to act at least in part at a nuclear level in altering the cellular concentration of this mRNA species. The rapidity of this change suggests that it may reflect a direct response to the binding of thyroid hormone to its nuclear receptor.
给甲状腺切除的大鼠注射甲状腺激素，会导致肝脏中编码斑点14的mRNA相对量迅速显著增加。斑点14是一种翻译产物，其近似相对分子质量为17,500，等电点为4.9。我们现已分离出一个cDNA克隆，其包含与这种甲状腺激素反应性mRNA同源的序列。发现两种长度相差200个核苷酸的不同mRNA种类能够与cDNA探针杂交。随着大鼠血浆甲状腺激素水平升高，这两种mRNA种类的相对浓度均成比例升高。在对甲状腺切除的大鼠进行甲状腺激素处理后20分钟，成熟mRNA水平出现最早变化。对核RNA的分析显示，有一种单一的高分子量种类与斑点14 mRNA同源。在注射甲状腺激素后10分钟，这种假定前体的核水平升高，这一时间早于成熟mRNA的最早变化。因此，甲状腺激素似乎至少部分在核水平发挥作用，以改变这种mRNA种类的细胞浓度。这种变化的迅速性表明，它可能反映了甲状腺激素与其核受体结合的直接反应。
