The size-wise nucleus: nuclear volume control in eukaryotes

Abstract

Eukaryotic cells have an "awareness" of their volume and organellar volumes, and maintain a nuclear size that is proportional to the total cell size. New studies in budding and fission yeast have examined the relationship between cell and nuclear volumes. It was found that the size of the nucleus remains proportional to cell size in a wide range of genetic backgrounds and growth conditions that alter cell volume and DNA content. Moreover, in multinucleated fission yeast cells, Neumann and Nurse (see p. 593 of this issue) found that the sizes of individual nuclei are controlled by the relative amount of cytoplasm surrounding each nucleus. These results highlight a role of the cytoplasm in nuclear size control.

Figure 1.

Schematic representation of the nuclear envelope/endoplasmic reticulum system of metazoan cells. The nucleoplasm is enclosed by the nuclear envelope (NE), which contains the inner nuclear membrane (INM), the outer nuclear membrane (ONM), the nuclear pore complex (NPC), and the lamina. The INM and ONM are continuous at the nuclear pores, and the ONM is continuous with the endoplasmic reticulum (ER), potentially allowing the flux of lipids and proteins to the inner and outer nuclear membranes during nuclear expansion. The yeast NE also contains NPCs and is continuous with the peripheral ER, but a functional counterpart to the metazoan lamina has not yet been described in yeast.