Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.
Epigenetics Chromatin. 2010 Jul 1;3(1):13. doi: 10.1186/1756-8935-3-13.
The physiological function of eukaryotic DNA occurs in the context of nucleosomal arrays that can expose or obscure defined segments of the genome. Certain DNA sequences are capable of strongly positioning a nucleosome in vitro, suggesting the possibility that favorable intrinsic signals might reproducibly structure chromatin segments. As high-throughput sequencing analyses of nucleosome coverage in vitro and in vivo have become possible, a vigorous debate has arisen over the degree to which intrinsic DNA:nucleosome affinities orchestrate the in vivo positions of nucleosomes, thereby controlling physical accessibility of specific sequences in DNA.
We describe here the in vivo consequences of placing a synthetic high-affinity nucleosome-positioning signal, the 601 sequence, into a DNA plasmid vector in mice. Strikingly, the 601 sequence was sufficient to position nucleosomes during an early phase after introduction of the DNA into the mice (when the plasmid vector transgene was active). This positioning capability was transient, with a loss of strong positioning at a later time point when the transgenes had become silent.
These results demonstrate an ability of DNA sequences selected solely for nucleosome affinity to organize chromatin in vivo, and the ability of other mechanisms to overcome these interactions in a dynamic nuclear environment.
真核生物 DNA 的生理功能发生在核小体阵列的情况下，核小体阵列可以暴露或隐藏基因组的定义片段。某些 DNA 序列能够在体外强烈定位核小体，这表明有利的固有信号可能能够重复地构建染色质片段。随着体外和体内核小体覆盖的高通量测序分析成为可能，关于固有 DNA：核小体亲和力在多大程度上协调体内核小体位置，从而控制 DNA 中特定序列的物理可及性的争论激烈。
我们在这里描述了在体内将合成的高亲和力核小体定位信号，即 601 序列，放置在小鼠中的 DNA 质粒载体中的后果。引人注目的是，601 序列足以在将 DNA 导入小鼠后（当质粒载体转基因活跃时）的早期阶段定位核小体。这种定位能力是短暂的，当转基因沉默时，强定位的能力会丧失。
这些结果表明，仅选择用于核小体亲和力的 DNA 序列有能力在体内组织染色质，并且其他机制有能力在动态核环境中克服这些相互作用。
