Landeros Adriana, Wallace Destiny A, Rahi Amit, Magdongon Christine B, Suraneni Praveen, Amin Mohammed A, Chakraborty Manas, Adam Stephen A, Foltz Daniel R, Varma Dileep
Dept. of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Ave Chicago, IL 60611.
Dept. of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, 303 E. Chicago Ave Chicago, IL 60611.
bioRxiv. 2023 Sep 26:2023.09.25.559341. doi: 10.1101/2023.09.25.559341.
Many Lamin A-associated proteins (LAAP's) that are key constituents of the nuclear envelope (NE), assemble at the "core" domains of chromosomes during NE reformation and mitotic exit. However, the identity and function of the chromosomal core domains remain ill-defined. Here, we show that a distinct section of the core domain overlaps with the centromeres/kinetochores of chromosomes during mitotic telophase. The core domain can thus be demarcated into a kinetochore proximal core (KPC) on one side of the segregated chromosomes and the kinetochore distal core (KDC) on the opposite side, close to the central spindle. We next tested if centromere assembly is connected to NE re-formation. We find that centromere assembly is markedly perturbed after inhibiting the function of LMNA and the core-localized LAAPs, BANF1 and Emerin. We also find that the LAAPs exhibit multiple biochemical interactions with the centromere and inner kinetochore proteins. Consistent with this, normal mitotic progression and chromosome segregation was severely impeded after inhibiting LAAP function. Intriguingly, the inhibition of centromere function also interferes with the assembly of LAAP components at the core domain, suggesting a mutual dependence of LAAP and centromeres for their assembly at the core domains. Finally, we find that the localization of key proteins involved in the centromeric loading of CENP-A, including the Mis18 complex and HJURP were markedly affected in LAAP-inhibited cells. Our evidence points to a model where LAAP assembly at the core domain serves a key function in loading new copies of centromeric proteins during or immediately after mitotic exit.
许多作为核膜（NE）关键组成部分的核纤层蛋白A相关蛋白（LAAP），在核膜重塑和有丝分裂退出过程中聚集在染色体的“核心”结构域。然而，染色体核心结构域的身份和功能仍不明确。在这里，我们表明，在有丝分裂末期，核心结构域的一个独特部分与染色体的着丝粒/动粒重叠。因此，核心结构域可以在分离染色体的一侧被划定为动粒近端核心（KPC），在另一侧靠近中央纺锤体的位置被划定为动粒远端核心（KDC）。接下来，我们测试了着丝粒组装是否与核膜重新形成相关。我们发现，在抑制LMNA以及核心定位的LAAP（BANF1和Emerin）的功能后，着丝粒组装受到显著干扰。我们还发现，LAAP与着丝粒和内动粒蛋白表现出多种生化相互作用。与此一致的是，在抑制LAAP功能后，正常的有丝分裂进程和染色体分离受到严重阻碍。有趣的是，着丝粒功能的抑制也会干扰LAAP组分在核心结构域的组装，这表明LAAP和着丝粒在核心结构域的组装上相互依赖。最后，我们发现，在LAAP抑制的细胞中，参与CENP - A着丝粒装载的关键蛋白（包括Mis18复合体和HJURP）的定位受到显著影响。我们的证据指向一个模型，即核心结构域处的LAAP组装在有丝分裂退出期间或之后立即加载新的着丝粒蛋白拷贝中起关键作用。
