An ESCRT grommet cooperates with a diffusion barrier to maintain nuclear integrity.

The molecular mechanisms by which the endosomal sorting complexes required for transport (ESCRT) proteins contribute to the integrity of the nuclear envelope (NE) barrier are not fully defined. We leveraged the single NE hole generated by mitotic extrusion of the Schizosaccharomyces pombe spindle pole body to reveal two modes of ESCRT function executed by distinct complements of ESCRT-III proteins, both dependent on CHMP7/Cmp7. A grommet-like function is required to restrict the NE hole in anaphase B, whereas replacement of Cmp7 by a sealing module ultimately closes the NE in interphase.

Non-random distribution of vacuoles in Schizosaccharomyces pombe.

A central question in eukaryotic cell biology asks, during cell division, how is the growth and distribution of organelles regulated to ensure each daughter cell receives an appropriate amount. For vacuoles in budding yeast, there are well described organelle-to-cell size scaling trends as well as inheritance mechanisms involving highly coordinated movements. It is unclear whether such mechanisms are necessary in the symmetrically dividing fission yeast, Schizosaccharomyces pombe, in which random partitioning may be utilized to distribute vacuoles to daughter cells.