Dynamic organization of mitotic chromosomes

- State-of-the-art technologies provide new insights into chromosome organization.
- Mitotic chromatids can be reconstituted in vitro using only six purified factors.
- HEAT subunits of condensin I are essential for chromosome axis assembly.
- Mutations in condensin subunits cause microcephaly and promote tumorigenesis.
- Interphase TADs may be linked to cytological bands on mitotic chromosomes.

The assembly of rod-shaped chromosomes during mitosis is an essential prerequisite for faithful segregation of genetic information into daughter cells. Despite the long history of chromosome research, it is only recently that we have acquired powerful approaches and crucial tools that help to unlock the secret of this seemingly complex process. In particular, in vitro assays, mammalian genetics, Hi-C analyses and computer simulations have provided valuable information during the past two years. These studies are now beginning to elucidate how the core components of mitotic chromosomes, namely, histones, topoisomerase IIα and condensins, cooperate with each other to convert very long stretches of DNA into rod-shaped chromosomes.