Farnham P J, Schimke R T
Mol Cell Biol. 1986 Feb;6(2):365-71. doi: 10.1128/mcb.6.2.365-371.1986.
The murine dihydrofolate reductase gene codes for mRNAs that differ in the length of their 3' untranslated region as well as in the length of their 5' leader sequence. In addition, the dihydrofolate reductase promoter functions bidirectionally, producing a series of RNAs from the opposite strand than the dihydrofolate reductase mRNAs. We have examined the production of these RNAs and their heterogeneous 5' and 3' termini as mouse 3T6 cells progress through a physiologically continuous cell cycle. We found that all of the transcripts traverse the cell cycle in a similar manner, increasing at the G1/S boundary without significantly changing their ratios relative to one another. We conclude that cell-cycle regulation of dihydrofolate reductase is achieved without recruiting new transcription initiation sites and without a change in polyadenylation sites. It appears that the mechanism responsible for the transcriptional cell-cycle regulation of the dihydrofolate reductase gene is manifested only by transiently increasing the efficiency of transcription at the dihydrofolate reductase promoter.
小鼠二氢叶酸还原酶基因编码的mRNA，其3'非翻译区长度以及5'前导序列长度存在差异。此外，二氢叶酸还原酶启动子具有双向功能，从与二氢叶酸还原酶mRNA相反的链产生一系列RNA。我们研究了在小鼠3T6细胞经历生理上连续的细胞周期时，这些RNA的产生及其异质性的5'和3'末端。我们发现所有转录本以相似的方式经历细胞周期，在G1/S边界增加，而彼此之间的比例没有显著变化。我们得出结论，二氢叶酸还原酶的细胞周期调控是在不招募新的转录起始位点且不改变聚腺苷酸化位点的情况下实现的。似乎负责二氢叶酸还原酶基因转录细胞周期调控的机制仅通过瞬时提高二氢叶酸还原酶启动子的转录效率来体现。
