在每个有丝分裂的最后阶段,核包膜的重组取决于纺锤体微管的分解,而不会破坏染色体的分离。这个过程涉及ESCRT-III复合物和痉挛的瞬时募集,一种微管切断AAA(与多种细胞活动相关的ATP酶)机械酶,晚期染色体。然而,剖析这些快速过程背后的机制,它可以在几分钟内完成,一直很难。这里,我们将速效化学抑制剂与活细胞成像相结合,发现纺锤体微管,随着痉挛的活动,调节在后期染色体上的痉挛灶的数量和寿命。出乎意料的是,抑制痉挛阻碍染色体分离,但不会改变CHMP4B的后期定位动力学,ESCRT-III蛋白,或增加γ-H2AX病灶,DNA损伤标记.我们表明,抑制痉挛会增加层粘连蛋白衬里的核微隧道的频率,其中可能包括穿透细胞核的微管。我们的发现表明,无法切断纺锤体微管会阻碍染色体分离,然而,重组核包膜可以在拓扑上容纳持续的微管,确保核DNA不受损或暴露于细胞质。
Nuclear envelope reassembly during the final stages of each mitosis depends on disassembling spindle microtubules without disrupting chromosome separation. This process involves the transient recruitment of the ESCRT-III complex and
spastin, a microtubule-severing AAA (ATPases associated with diverse cellular activities) mechanoenzyme, to late-anaphase chromosomes. However, dissecting mechanisms underlying these rapid processes, which can be completed within minutes, has been difficult. Here, we combine fast-acting chemical inhibitors with live-cell imaging and find that spindle microtubules, along with
spastin activity, regulate the number and lifetimes of
spastin foci at anaphase chromosomes. Unexpectedly,
spastin inhibition impedes chromosome separation, but does not alter the anaphase localization dynamics of CHMP4B, an ESCRT-III protein, or increase γ-H2AX foci, a DNA damage marker. We show
spastin inhibition increases the frequency of lamin-lined nuclear microtunnels that can include microtubules penetrating the nucleus. Our findings suggest failure to sever spindle microtubules impedes chromosome separation, yet reforming nuclear envelopes can topologically accommodate persistent microtubules ensuring nuclear DNA is not damaged or exposed to cytoplasm.