Nuclear Envelope Assembly and Disassembly During the Cell Cycle

Abstract

Abstract The nuclear envelope of metazoa breaks down at the onset of mitosis and reassembles at the end of mitosis. This process is mainly controlled by the cyclin‐dependent kinase that phosphorylates inner nuclear membrane (INM) proteins to disrupt their association with chromatin and to disintegrate the nuclear lamina. Upon nuclear envelope breakdown, the nuclear membrane and integral nuclear membrane proteins retract into the endoplasmic reticulum (ER), whereas other peripheral nuclear membrane proteins and some components of the nuclear pore complex become disperse in the cytosol. At late anaphase, inactivation of the cyclin‐dependent kinase and dephosphorylation of INM proteins allow these proteins to bind the chromatin and brings the ER membrane to the chromatin surface to initiate nuclear envelope assembly around the compact chromosome mass. The nuclear envelope disassembly and assembly are thus coordinated with the segregation of sister chromatids in each cell division cycle to maintain genome stability. Key Concepts: The nuclear envelope is a dynamic structure that is continuous with the ER. The INM proteins associate with and organise the chromatin. The disassembly of nuclear envelope is triggered by the cyclin‐dependent kinase at the onset of mitosis. Phosphorylation of INM proteins disrupts their interaction with chromatin. Nuclear envelope breakdown is essential for sister chromatid segregation. Integral nuclear membrane proteins diffuse into the ER after nuclear envelope breakdown. The nuclear envelope reassembles around compact chromosome mass at late anaphase/telophase. Nuclear envelope reassembly is mediated by multiple interactions of the INM proteins with chromatin. Dephosphorylation of INM proteins at late anaphase/telophase is required for nuclear envelope reassembly.