Disassembly of the nuclear envelope must occur for kinetochore microtubules to form in animal cells. This disassembly of nuclear envelope is triggered by the cyclin-dependent kinase at the onset of mitosis. The 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.