Enhancer Regulation of Transcriptional Bursting Parameters Revealed by Forced Chromatin Looping.
Enhancer Regulation of Transcriptional Bursting Parameters Revealed by Forced Chromatin Looping.
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DOI：
10.1016/j.molcel.2016.03.007
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发表时间：
2016-04-21
期刊：
影响因子：
16
通讯作者：
Blobel GA
中科院分区：
文献类型：
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作者：
Bartman CR;Hsu SC;Hsiung CC;Raj A;Blobel GA
哺乳动物的基因不是连续地转录RNA，而是连续地转录。转录输出可以通过改变爆发分数或爆发大小来调节，但调控元件如何控制爆发参数仍不清楚。单分子RNA FISH实验表明，β-珠蛋白增强子（LCR）主要通过适度刺激β-珠蛋白基因的爆发大小来增加β-珠蛋白基因的转录爆发部分。为了具体测量远程染色质接触对转录破裂的影响，我们构建了LCR-β-珠蛋白启动子染色质环。我们观察到，提高接触频率会增加爆发分数，但不会增加爆发尺寸。在两个发育不同的lcr调节珠蛋白基因以顺式共转录的细胞中，两个基因的爆发大小是相似的。然而，两种基因的等位基因共转录在统计上是不利的，这表明lcr -基因接触是互斥的。这些结果与β型珠蛋白基因之间的LCR接触竞争一致，表明LCR启动子环的形成和释放具有快速动力学。
Mammalian genes do not transcribe RNA continuously but in bursts. Transcriptional output can be modulated by altering burst fraction or burst size, but how regulatory elements control bursting parameters remains unclear. Single-molecule RNA FISH experiments revealed that the β-globin enhancer (LCR) predominantly augments transcriptional burst fraction of the β-globin gene with modest stimulation of burst size. To specifically measure the impact of long range chromatin contacts on transcriptional bursting, we forced an LCR-β-globin promoter chromatin loop. We observed that raising contact frequencies increases burst fraction but not burst size. In cells in which two developmentally distinct LCR-regulated globin genes are cotranscribed in cis, burst sizes of both genes are comparable. However, allelic co-transcription of both genes is statistically disfavored, suggesting mutually exclusive LCR-gene contacts. These results are consistent with competition between the β-type globin genes for LCR contacts and suggest that LCR-promoter loops are formed and released with rapid kinetics.