Butin-Israeli Veronika, Adam Stephen A, Jain Nikhil, Otte Gabriel L, Neems Daniel, Wiesmüller Lisa, Berger Shelly L, Goldman Robert D
Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Epigenetics Program, Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA.
Mol Cell Biol. 2015 Mar;35(5):884-98. doi: 10.1128/MCB.01145-14. Epub 2014 Dec 22.
Nuclear lamins play important roles in the organization and structure of the nucleus; however, the specific mechanisms linking lamin structure to nuclear functions are poorly defined. We demonstrate that reducing nuclear lamin B1 expression by short hairpin RNA-mediated silencing in cancer cell lines to approximately 50% of normal levels causes a delay in the cell cycle and accumulation of cells in early S phase. The S phase delay appears to be due to the stalling and collapse of replication forks. The double-strand DNA breaks resulting from replication fork collapse were inefficiently repaired, causing persistent DNA damage signaling and the assembly of extensive repair foci on chromatin. The expression of multiple factors involved in DNA replication and repair by both nonhomologous end joining and homologous repair is misregulated when lamin B1 levels are reduced. We further demonstrate that lamin B1 interacts directly with the promoters of some genes associated with DNA damage response and repair, including BRCA1 and RAD51. Taken together, the results suggest that the maintenance of lamin B1 levels is required for DNA replication and repair through regulation of the expression of key factors involved in these essential nuclear functions.
核纤层蛋白在细胞核的组织和结构中发挥着重要作用；然而，将核纤层蛋白结构与核功能联系起来的具体机制却知之甚少。我们证明，通过短发夹RNA介导的沉默作用，将癌细胞系中的核纤层蛋白B1表达降低至正常水平的约50%，会导致细胞周期延迟，并使细胞在S期早期积累。S期延迟似乎是由于复制叉的停滞和崩溃所致。复制叉崩溃导致的双链DNA断裂修复效率低下，从而引起持续的DNA损伤信号传导以及染色质上广泛修复位点的组装。当核纤层蛋白B1水平降低时，参与非同源末端连接和同源修复的DNA复制及修复的多种因子的表达会发生失调。我们进一步证明，核纤层蛋白B1直接与一些与DNA损伤反应和修复相关的基因的启动子相互作用，包括BRCA1和RAD51。综上所述，这些结果表明，通过调节参与这些重要核功能的关键因子的表达，维持核纤层蛋白B1的水平对于DNA复制和修复是必需的。
