Biology, Main Building, First Floor, Room#B-216, Indian Institute of Science Education and Research (IISER), Pune, Dr Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India.
Nucleic Acids Res. 2018 Jun 20;46(11):5561-5586. doi: 10.1093/nar/gky288.
Cells perceive and relay external mechanical forces into the nucleus through the nuclear envelope. Here we examined the effect of lowering substrate stiffness as a paradigm to address the impact of altered mechanical forces on nuclear structure-function relationships. RNA sequencing of cells on softer matrices revealed significant transcriptional imbalances, predominantly in chromatin associated processes and transcriptional deregulation of human Chromosome 1. Furthermore, 3-Dimensional fluorescence in situ hybridization (3D-FISH) analyses showed a significant mislocalization of Chromosome 1 and 19 Territories (CT) into the nuclear interior, consistent with their transcriptional deregulation. However, CT18 with relatively lower transcriptional dysregulation, also mislocalized into the nuclear interior. Furthermore, nuclear Lamins that regulate chromosome positioning, were mislocalized into the nuclear interior in response to lowered matrix stiffness. Notably, Lamin B2 overexpression retained CT18 near the nuclear periphery in cells on softer matrices. While, cells on softer matrices also activated emerin phosphorylation at a novel Tyr99 residue, the inhibition of which in a phospho-deficient mutant (emerinY99F), selectively retained chromosome 18 and 19 but not chromosome 1 territories at their conserved nuclear locations. Taken together, emerin functions as a key mechanosensor, that modulates the spatial organization of chromosome territories in the interphase nucleus.
细胞通过核膜将外部机械力感知并传递到核内。在这里，我们研究了降低基质硬度作为范例，以解决机械力变化对核结构-功能关系的影响。在较软基质上的细胞的 RNA 测序显示出显著的转录失衡，主要在染色质相关过程和人类 1 号染色体的转录失调。此外，3D 荧光原位杂交（3D-FISH）分析显示 1 号和 19 号染色体区室（CT）显著向核内错位，与其转录失调一致。然而，相对转录失调较低的 CT18 也向核内错位。此外，调节染色体定位的核层粘连蛋白在响应基质硬度降低时向核内错位。值得注意的是，Lamin B2 的过表达使 CT18 在较软基质上的细胞靠近核周。然而，较软基质上的细胞还在新型 Tyr99 残基处激活了 emerin 的磷酸化，在磷酸化缺陷突变体（emerinY99F）中抑制 emerin 的磷酸化，选择性地将染色体 18 和 19 保留在其保守的核位置，但不保留染色体 1 的区室。总之，emerin 作为一种关键的机械感受器，调节着间期核中染色体区室的空间组织。
