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.

Four-dimensional analyses show that replication compartments are clonal factories in which Epstein-Barr viral DNA amplification is coordinated.

Herpesviruses must amplify their DNA to load viral particles and they do so in replication compartments. The development and functions of replication compartments during DNA amplification are poorly understood, though. Here we examine 2 functionally distinct replicons in the same cells to dissect DNA amplification within replication compartments.