A mitotic chromatin phase transition prevents perforation by microtubules.

Dividing eukaryotic cells package extremely long chromosomal DNA molecules into discrete bodies to enable microtubule-mediated transport of one genome copy to each of the newly forming daughter cells. Assembly of mitotic chromosomes involves DNA looping by condensin and chromatin compaction by global histone deacetylation. Although condensin confers mechanical resistance to spindle pulling forces, it is not known how histone deacetylation affects material properties and, as a consequence, segregation mechanics of mitotic chromosomes.

Chromosome clustering by Ki-67 excludes cytoplasm during nuclear assembly.

Gene expression in eukaryotes requires the effective separation of nuclear transcription and RNA processing from cytosolic translation. This separation is achieved by the nuclear envelope, which controls the exchange of macromolecules through nuclear pores. During mitosis, however, the nuclear envelope in animal and plant cells disassembles, allowing cytoplasmic and nuclear components to intermix.