The A- and B-type nuclear lamin networks: microdomains involved in chromatin organization and transcription
The A- and B-type nuclear lamin networks: microdomains involved in chromatin organization and transcription
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DOI：
10.1101/gad.1735208
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发表时间：
2008-12-15
影响因子：
10.5
通讯作者：
Goldman, Robert D.
中科院分区：
文献类型：
--
作者：
Shimi, Takeshi;Pfleghaar, Katrin;Goldman, Robert D.
核层蛋白在染色质的复制、转录和表观遗传修饰中起着调节作用。然而，对这些层粘连蛋白功能的机制却知之甚少。我们用荧光相关光谱(FCS)研究了A型和B型板层在板层中形成分离的但相互作用的稳定网络，并在核质中具有不同的迁移率。抑制层蛋白B1(LB1)的表达显著增加了板层网络的大小和核质层蛋白A(LA)的流动性。板网大小的变化与Lb2缺乏的富含LA/C的核膜泡的形成有关。显微解剖滤过泡的比较基因组杂交(CGH)分析、荧光原位杂交(FISH)和修饰组蛋白的免疫荧光定位表明，富含基因的常染色质与LA/C滤过泡有关。过度磷酸化的RNA聚合酶II(POL II)和激活转录的组蛋白标记的丰富表明，水泡在转录上是活跃的。然而，体内RNA标记表明转录减少，这表明富含LA/C的微环境导致Pol II的启动子近端停滞。我们认为不同的Lamins被组织成独立的、但相互作用的微域，LB1对它们的组织是必不可少的。我们的证据表明，染色质的组织和调节受到这些层蛋白微域之间的相互联系的影响。
The nuclear lamins function in the regulation of replication, transcription, and epigenetic modifications of chromatin. However, the mechanisms responsible for these lamin functions are poorly understood. We demonstrate that A- and B-type lamins form separate, but interacting, stable meshworks in the lamina and have different mobilities in the nucleoplasm as determined by fluorescence correlation spectroscopy (FCS). Silencing lamin B1 (LB1) expression dramatically increases the lamina meshwork size and the mobility of nucleoplasmic lamin A (LA). The changes in lamina mesh size are coupled to the formation of LA/C-rich nuclear envelope blebs deficient in LB2. Comparative genomic hybridization (CGH) analyses of microdissected blebs, fluorescence in situ hybridization (FISH), and immunofluorescence localization of modified histones demonstrate that gene-rich euchromatin associates with the LA/C blebs. Enrichment of hyperphosphorylated RNA polymerase II (Pol II) and histone marks for active transcription suggest that blebs are transcriptionally active. However, in vivo labeling of RNA indicates that transcription is decreased, suggesting that the LA/C-rich microenvironment induces promoter proximal stalling of Pol II. We propose that different lamins are organized into separate, but interacting, microdomains and that LB1 is essential for their organization. Our evidence suggests that the organization and regulation of chromatin are influenced by interconnections between these lamin microdomains.