Stochastic mRNA synthesis in mammalian cells.
Stochastic mRNA synthesis in mammalian cells.
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DOI：
10.1371/journal.pbio.0040309
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发表时间：
2006-10
期刊：
影响因子：
9.8
通讯作者：
Tyagi S
中科院分区：
文献类型：
--
作者：
Raj A;Peskin CS;Tranchina D;Vargas DY;Tyagi S
在基因同质的群体中，单个细胞已被发现会表达不同数量的特定蛋白质分子。我们通过对稳定整合到细胞基因组中的报告基因所产生的mRNA单个分子进行计数，研究了哺乳动物细胞中这些差异的起源。我们发现每个细胞中存在的mRNA分子数量存在巨大差异。这些差异的产生是因为mRNA是在基因从非活性状态转变为活性状态时开始、并在其转变回非活性状态时结束的短暂但强烈的转录爆发中合成的。我们表明这些转变本质上是随机的，而不是由于诸如转录激活因子水平等全局的、外在的因素。此外，基因激活会导致更广泛的基因组位点内所有基因的爆发式表达。我们还发现自然基因的合成中也存在爆发情况。mRNA表达的爆发可通过缓慢的蛋白质降解速率在蛋白质水平上得到缓冲。我们开发了一个基因激活和失活的随机模型来解释爆发的统计特性。该模型表明，增加转录因子的水平会增加爆发的平均规模，而不是其频率。这些结果表明哺乳动物细胞中的基因表达受到巨大的、本质上随机的波动影响，并引发了关于细胞在面对这种噪声时如何能够发挥功能的问题。
对给定基因产生的单个mRNA分子进行计数，为哺乳动物细胞间基因表达的随机波动提供了证据。
Individual cells in genetically homogeneous populations have been found to express different numbers of molecules of specific proteins. We investigated the origins of these variations in mammalian cells by counting individual molecules of mRNA produced from a reporter gene that was stably integrated into the cell's genome. We found that there are massive variations in the number of mRNA molecules present in each cell. These variations occur because mRNAs are synthesized in short but intense bursts of transcription beginning when the gene transitions from an inactive to an active state and ending when they transition back to the inactive state. We show that these transitions are intrinsically random and not due to global, extrinsic factors such as the levels of transcriptional activators. Moreover, the gene activation causes burst-like expression of all genes within a wider genomic locus. We further found that bursts are also exhibited in the synthesis of natural genes. The bursts of mRNA expression can be buffered at the protein level by slow protein degradation rates. A stochastic model of gene activation and inactivation was developed to explain the statistical properties of the bursts. The model showed that increasing the level of transcription factors increases the average size of the bursts rather than their frequency. These results demonstrate that gene expression in mammalian cells is subject to large, intrinsically random fluctuations and raise questions about how cells are able to function in the face of such noise. Counting individual mRNA molecules produced by a given gene provides evidence of random fluctuations in mammalian gene expression from cell to cell.