Vega-Palas M A, Ferl R J
Horticultural Sciences Department, University of Florida, Gainesville 32611, USA.
Plant Cell. 1995 Nov;7(11):1923-32. doi: 10.1105/tpc.7.11.1923.
The alcohol dehydrogenase (Adh) gene from Arabidopsis shows enhanced sensitivity to DNase I in cells that express the gene. This generalized sensitivity to DNase I is demarcated by position -500 on the 5' side and the end of the mRNA on the 3' side. Thus, the gene defined as the promoter and mRNA coding region corresponds very closely in size with the gene defined as a nuclease-sensitive domain. This is a remarkably close correspondence between a sensitive domain and a eukaryotic transcriptional unit, because previously reported DNase I-sensitive domains include large regions of DNA that are not transcribed. Nucleosomes are present in the coding region of the Adh gene when it is expressed, indicating that the transcriptional elongation process causes nucleosome disruption rather than release of nucleosomes from the coding region. In addition, the regulatory region contains a loosely positioned nucleosome that is separated from adjacent nucleosomes by internucleosomic DNA segments longer than the average linker DNA in bulk chromatin. This specific array of nucleosomes coexists with bound transcription factors that could contribute to the organization of the nucleosome arrangement. These results enhance our understanding of the complex interactions among DNA, nucleosomes, and transcription factors during gene expression in plants.
拟南芥中的乙醇脱氢酶（Adh）基因在表达该基因的细胞中对DNase I表现出增强的敏感性。这种对DNase I的普遍敏感性在5'端由-500位置界定，在3'端由mRNA的末端界定。因此，被定义为启动子和mRNA编码区的基因在大小上与被定义为核酸酶敏感结构域的基因非常接近。这是一个敏感结构域与真核转录单元之间非常紧密的对应关系，因为先前报道的DNase I敏感结构域包括未转录的大片段DNA区域。当Adh基因表达时，核小体存在于其编码区，这表明转录延伸过程导致核小体破坏，而不是核小体从编码区释放。此外，调控区含有一个定位松散的核小体，它与相邻核小体之间由比整体染色质中平均连接DNA长的核小体间DNA片段隔开。这种特定的核小体阵列与可能有助于核小体排列组织的结合转录因子共存。这些结果增进了我们对植物基因表达过程中DNA、核小体和转录因子之间复杂相互作用的理解。
