Chen Keshi, Long Qi, Wang Tao, Zhao Danyun, Zhou Yanshuang, Qi Juntao, Wu Yi, Li Shengbiao, Chen Chunlan, Zeng Xiaoming, Yang Jianguo, Zhou Zisong, Qin Weiwen, Liu Xiyin, Li Yuxing, Li Yingying, Huang Xiaofen, Qin Dajiang, Chen Jiekai, Pan Guangjin, Schöler Hans R, Xu Guoliang, Liu Xingguo, Pei Duanqing
Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.
Department for Cell and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany.
EMBO Rep. 2016 Nov;17(11):1641-1656. doi: 10.15252/embr.201642402. Epub 2016 Oct 4.
Reprogramming of somatic cells to induced pluripotent stem cells rewrites the code of cell fate at the chromatin level. Yet, little is known about this process physically. Here, we describe a fluorescence recovery after photobleaching method to assess the dynamics of heterochromatin/euchromatin and show significant heterochromatin loosening at the initial stage of reprogramming. We identify growth arrest and DNA damage-inducible protein a (Gadd45a) as a chromatin relaxer in mouse embryonic fibroblasts, which also enhances somatic cell reprogramming efficiency. We show that residue glycine 39 (G39) in Gadd45a is essential for interacting with core histones, opening chromatin and enhancing reprogramming. We further demonstrate that Gadd45a destabilizes histone-DNA interactions and facilitates the binding of Yamanaka factors to their targets for activation. Our study provides a method to screen factors that impact on chromatin structure in live cells, and identifies Gadd45a as a chromatin relaxer.
将体细胞重编程为诱导多能干细胞会在染色质水平上改写细胞命运的编码。然而，对于这一过程的物理机制我们知之甚少。在此，我们描述了一种光漂白后荧光恢复方法，用于评估异染色质/常染色质的动力学，并显示在重编程的初始阶段异染色质显著松弛。我们鉴定出生长停滞和DNA损伤诱导蛋白α（Gadd45a）是小鼠胚胎成纤维细胞中的一种染色质松弛剂，它还能提高体细胞重编程效率。我们表明，Gadd45a中的甘氨酸39（G39）残基对于与核心组蛋白相互作用、打开染色质以及增强重编程至关重要。我们进一步证明，Gadd45a会破坏组蛋白与DNA的相互作用，并促进山中因子与其靶标的结合以实现激活。我们的研究提供了一种在活细胞中筛选影响染色质结构的因子的方法，并鉴定出Gadd45a是一种染色质松弛剂。
