De-regulated expression of the BRG1 chromatin remodeling factor in bone marrow mesenchymal stromal cells induces senescence associated with the silencing of NANOG and changes in the levels of chromatin proteins
De-regulated expression of the BRG1 chromatin remodeling factor in bone marrow mesenchymal stromal cells induces senescence associated with the silencing of NANOG and changes in the levels of chromatin proteins
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DOI：
10.4161/15384101.2014.995053
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发表时间：
2015-04-15
期刊：
影响因子：
4.3
通讯作者：
Galderisi, Umberto
中科院分区：
文献类型：
--
作者：
Squillaro, Tiziana;Severino, Valeria;Galderisi, Umberto
干细胞具有特殊的染色质结构，这有助于其独特的性质，包括未定型状态，多能性和自我更新。我们分析了SWI/SNF染色质重塑复合物在间充质基质细胞（MSC）中通过沉默和上调BRG 1（复合物的ATP酶亚基）的失调的影响。BRG 1表达的改变促进了MSC的衰老，同时抑制了NANOG转录，这是控制干细胞功能的转录回路的一部分。为了深入了解NANOG被沉默的方式，我们评估了去调控的BRG 1表达如何影响NANOG启动子上激活子和阻遏子的结合。我们在NANOG启动子上发现了4个E2 F结合基序，这些基序可以被RB 1和RB 2/P130占据。这些是视网膜母细胞瘤基因家族的成员。在BRG 1沉默的MSC中，2种视网膜母细胞瘤蛋白的相对结合增加，这与DNMT 1的募集有关。这诱导了NANOG启动子上CpG的甲基化。相反，当存在高水平的BRG 1时，相同的E2 F结合基序是BRG 1的对接位点，其诱导染色质压缩而没有CpG甲基化，但组蛋白脱乙酰化增加，与E2 F结合位点上HDAC 1的存在相关。除了NANOG表达的急剧调节外，我们通过蛋白质组学分析证明，SWI/SNF功能的失调影响了组蛋白和其他参与“核结构”的核蛋白的表达，这表明BRG 1可能充当基因表达的全局调节器。
Stem cells have a peculiar chromatin architecture that contributes to their unique properties, including uncommitted status, multi/pluripotency and self-renewal. We analyzed the effect of the de-regulation of the SWI/SNF chromatin remodeling complex in mesenchymal stromal cells (MSC) through the silencing and up-regulation of BRG1, which is the ATPase subunit of the complex. The altered expression of BRG1 promoted the senescence of MSC with suppression of the NANOG transcription, which is part of the transcriptional circuitry governing stem cell functions. To gain insight on the way NANOG was silenced, we evaluated how the de-regulated BRG1 expression affect the binding of activators and repressors on the NANOG promoter. We found 4 E2F binding motifs on NANOG promoter, which can be occupied by RB1 and RB2/P130. These are members of the retinoblastoma gene family. In MSC with a silenced BRG1, the relative binding of the 2 retinoblastoma proteins increased, and this was associated with the recruitment of DNMT1. This induced the methylation of CpG on the NANOG promoter. Opposingly, when a high level of BRG1 was present, the same E2F binding motifs were docking sites for BRG1, which induced chromatin compaction without CpG methylation but with increased histone deacetylation, associated with the presence of HDAC1 on E2F binding sites. Besides the sharp regulation of the NANOG expression, we evidenced, through proteomic analysis, that the de-regulation of the SWI/SNF function affected the expression of histones and other nuclear proteins involved in "nuclear architecture," suggesting that BRG1 may act as global regulator of gene expression.