Golding Ido, Paulsson Johan, Zawilski Scott M, Cox Edward C
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Cell. 2005 Dec 16;123(6):1025-36. doi: 10.1016/j.cell.2005.09.031.
Protein levels have been shown to vary substantially between individual cells in clonal populations. In prokaryotes, the contribution to such fluctuations from the inherent randomness of gene expression has largely been attributed to having just a few transcripts of the corresponding mRNAs. By contrast, eukaryotic studies tend to emphasize chromatin remodeling and burst-like transcription. Here, we study single-cell transcription in Escherichia coli by measuring mRNA levels in individual living cells. The results directly demonstrate transcriptional bursting, similar to that indirectly inferred for eukaryotes. We also measure mRNA partitioning at cell division and correlate mRNA and protein levels in single cells. Partitioning is approximately binomial, and mRNA-protein correlations are weaker earlier in the cell cycle, where cell division has recently randomized the relative concentrations. Our methods further extend protein-based approaches by counting the integer-valued number of transcript with single-molecule resolution. This greatly facilitates kinetic interpretations in terms of the integer-valued random processes that produce the fluctuations.
已表明克隆群体中各个细胞之间的蛋白质水平差异很大。在原核生物中,基因表达内在随机性对这种波动的贡献很大程度上归因于相应mRNA仅有少数转录本。相比之下,真核生物研究倾向于强调染色质重塑和爆发式转录。在这里,我们通过测量单个活细胞中的mRNA水平来研究大肠杆菌中的单细胞转录。结果直接证明了转录爆发,类似于对真核生物间接推断的情况。我们还测量了细胞分裂时mRNA的分配,并关联了单细胞中的mRNA和蛋白质水平。分配大致呈二项式,并且在细胞周期中较早阶段,mRNA与蛋白质的相关性较弱,此时细胞分裂最近使相对浓度随机化。我们的方法通过以单分子分辨率对整数值的转录本数量进行计数,进一步扩展了基于蛋白质的方法。这极大地促进了根据产生波动的整数值随机过程进行动力学解释。