Dixon Charles R, Platani Melpomeni, Makarov Alexandr A, Schirmer Eric C
The Wellcome Trust Centre for Cell Biology, University of Edinburgh, Kings Buildings, Swann 5.22, Max Born Crescent, Edinburgh EH9 3BF, UK.
Cells. 2017 Mar 25;6(2):9. doi: 10.3390/cells6020009.
Lamins form a scaffold lining the nucleus that binds chromatin and contributes to spatial genome organization; however, due to the many other functions of lamins, studies knocking out or altering the lamin polymer cannot clearly distinguish between direct and indirect effects. To overcome this obstacle, we specifically targeted the mapped histone-binding site of A/C lamins by microinjecting antibodies specific to this region predicting that this would make the genome more mobile. No increase in chromatin mobility was observed; however, interestingly, injected cells failed to go through mitosis, while control antibody-injected cells did. This effect was not due to crosslinking of the lamin polymer, as Fab fragments also blocked mitosis. The lack of genome mobility suggested other lamin-chromatin interactions. To determine what these might be, mini-lamin A constructs were expressed with or without the histone-binding site that assembled into independent intranuclear structures. HP1, CenpB and PML proteins accumulated at these structures for both constructs, indicating that other sites supporting chromatin interactions exist on lamin A. Together, these results indicate that lamin A-chromatin interactions are highly redundant and more diverse than generally acknowledged and highlight the importance of trying to experimentally separate their individual functions.
核纤层蛋白形成一个衬于细胞核内的支架，它与染色质结合并有助于基因组的空间组织；然而，由于核纤层蛋白具有许多其他功能，敲除或改变核纤层蛋白聚合物的研究无法明确区分直接和间接效应。为了克服这一障碍，我们通过显微注射针对该区域的特异性抗体，专门靶向A/C型核纤层蛋白的映射组蛋白结合位点，预计这将使基因组更具流动性。未观察到染色质流动性增加；然而，有趣的是，注射抗体的细胞未能进入有丝分裂，而注射对照抗体的细胞则可以。这种效应不是由于核纤层蛋白聚合物的交联，因为Fab片段也会阻断有丝分裂。基因组缺乏流动性表明存在其他核纤层蛋白 - 染色质相互作用。为了确定这些相互作用可能是什么，表达了带有或不带有组蛋白结合位点的微型核纤层蛋白A构建体，它们组装成独立的核内结构。对于这两种构建体，HP1、CenpB和PML蛋白都在这些结构上积累，表明核纤层蛋白A上存在其他支持染色质相互作用的位点。总之，这些结果表明核纤层蛋白A - 染色质相互作用高度冗余且比普遍认为的更多样化，并强调了尝试通过实验分离其各自功能的重要性。
