Mitotic chromosome assembly despite nucleosome depletion in Xenopus egg extracts

Abstract

Packaging without nucleosomes The fundamental compaction of DNA in chromosomes is thought to start with the wrapping of DNA around nucleosomes, but is nucleosome wrapping required for the condensation of mitotic chromosomes? Shintomi et al. combined Xenopus egg extracts and mouse sperm nuclei and found that chromosome-like structures could be assembled in the near-complete absence of nucleosomes (see the Perspective by Kakui and Uhlmann). These “nucleosome-depleted” chromosomes were composed of condensin-enriched discrete axes and poorly organized chromatin loops. This finding challenges the textbook view of mitotic chromosome organization. Science , this issue p. 1284 ; see also p. 1233