Cherry S R, Baltimore D
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Proc Natl Acad Sci U S A. 1999 Sep 14;96(19):10788-93. doi: 10.1073/pnas.96.19.10788.
V(D)J recombination substrate choice is regulated to ensure that the appropriate gene segments are rearranged during lymphocyte development. It has been proposed that regulation of substrate usage is determined by changes in accessibility of the DNA targets. We show that Rag-mediated recombination of an episomal substrate in cells is affected by its packaging into chromatin. Chromatinized substrates were inefficiently rearranged, and methylation further reduced recombination. Disruption of nucleosomes by using butyrate on methylated substrates was sufficient to activate recombination, and dexamethasone could activate recombination in the absence of detectable transcription. Therefore, chromatin structure, and its manipulation by altering nucleosome positioning, can directly affect recombination efficiencies.
V(D)J 重组底物的选择受到调控,以确保在淋巴细胞发育过程中适当的基因片段发生重排。有人提出,底物使用的调控是由 DNA 靶点可及性的变化决定的。我们发现,细胞中附加体质底物的 Rag 介导的重组受到其包装进染色质的影响。染色质化的底物重排效率低下,甲基化进一步降低重组。在甲基化底物上使用丁酸盐破坏核小体足以激活重组,并且地塞米松在没有可检测到的转录的情况下也可以激活重组。因此,染色质结构及其通过改变核小体定位的操纵可以直接影响重组效率。