Anderson Daniel J, Vargas Jesse D, Hsiao Joshua P, Hetzer Martin W
Salk Institute for Biological Studies, Molecular and Cell Biology Laboratory, La Jolla, CA 92037, USA.
J Cell Biol. 2009 Jul 27;186(2):183-91. doi: 10.1083/jcb.200901106. Epub 2009 Jul 20.
Formation of the nuclear envelope (NE) around segregated chromosomes occurs by the reshaping of the endoplasmic reticulum (ER), a reservoir for disassembled nuclear membrane components during mitosis. In this study, we show that inner nuclear membrane proteins such as lamin B receptor (LBR), MAN1, Lap2beta, and the trans-membrane nucleoporins Ndc1 and POM121 drive the spreading of ER membranes into the emerging NE via their capacity to bind chromatin in a collaborative manner. Despite their redundant functions, decreasing the levels of any of these trans-membrane proteins by RNAi-mediated knockdown delayed NE formation, whereas increasing the levels of any of them had the opposite effect. Furthermore, acceleration of NE formation interferes with chromosome separation during mitosis, indicating that the time frame over which chromatin becomes membrane enclosed is physiologically relevant and regulated. These data suggest that functionally distinct classes of chromatin-interacting membrane proteins, which are present at nonsaturating levels, collaborate to rapidly reestablish the nuclear compartment at the end of mitosis.
围绕分离的染色体形成核膜（NE）是通过内质网（ER）的重塑实现的，内质网是有丝分裂期间核膜组件拆卸后的储存库。在本研究中，我们表明，诸如核纤层蛋白B受体（LBR）、MAN1、Lap2β等内核膜蛋白以及跨膜核孔蛋白Ndc1和POM121，通过它们以协同方式结合染色质的能力，驱动内质网膜向新形成的核膜扩散。尽管它们具有冗余功能，但通过RNA干扰介导的敲低降低这些跨膜蛋白中任何一种的水平都会延迟核膜形成，而增加其中任何一种的水平则会产生相反的效果。此外，核膜形成的加速会干扰有丝分裂期间的染色体分离，这表明染色质被膜包裹的时间框架在生理上是相关的且受到调控。这些数据表明，功能不同的几类与染色质相互作用的膜蛋白，以不饱和水平存在，它们协同作用，在有丝分裂末期迅速重新建立核区室。
