Ross I L, Browne C M, Hume D A
Centre for Molecular Biology and Biotechnology, University of Queensland, Brisbane, Australia.
Immunol Cell Biol. 1994 Apr;72(2):177-85. doi: 10.1038/icb.1994.26.
Experimental evidence is presented indicating that the expression of a lacZ reporter gene driven by the HIV-1 long terminal repeat in a series of stably transfected, cloned macrophage cell lines occurs in a very small proportion of cells. The proportion of cells expressing lacZ, rather than the level of expression in each cell, is regulated by external stimuli such as LPS and phorbol ester. Based upon these and published data we propose that transcription in eukaryotic cells occurs in short pulses interspersed by long periods of inactivity of indeterminate duration. Transcriptional regulation is envisaged as involving changes in the probability rather than the rate of transcription. A probabilistic model of transcription may explain many biological phenomena, such as stem cell division and clonogenic activity, heterogeneous gene expression among clonal cell populations, retroviral latency and cell cycle progression, which appear to involve stochastic decisions.
实验证据表明，在一系列稳定转染、克隆的巨噬细胞系中，由HIV-1长末端重复序列驱动的lacZ报告基因仅在极小比例的细胞中表达。表达lacZ的细胞比例，而非每个细胞中的表达水平，受LPS和佛波酯等外部刺激的调控。基于这些以及已发表的数据，我们提出真核细胞中的转录以短脉冲形式发生，其间穿插着时长不定的长时间无活性状态。转录调控被设想为涉及转录概率而非转录速率的变化。转录的概率模型或许可以解释许多生物学现象，比如干细胞分裂和克隆形成活性、克隆细胞群体间的异质基因表达、逆转录病毒潜伏以及细胞周期进程，这些现象似乎都涉及随机决策。
