When you watch a cell going through mitosis, it looks like a smooth ballet performance—grace with impeccable timing and synchrony. In reality, there is a lot going on within the cell to make mitosis progress so smoothly, just like the ballet dancers’ actual physical exertion and concentration. Today’s image is from a paper that describes the timely removal of proteins from the nuclear envelope during mitosis.
The nuclear envelope (NE) is a double membrane that separates the cell’s genome from the rest of the cell, and permits transport of material into and out of the nucleus through multi-protein complexes called nuclear pores. During mitosis, the NE breaks down in order to allow chromosomes to attach to the mitotic spindle. Prior to NE breakdown, the nucleoporins that make up the nuclear pore complexes must be dissociated from the NE. A recent paper describes the timely removal of the nucleoporin NPP-3 near centrosomes at the onset of mitosis in early worm embryos. Hachet and colleagues found that centrosomes and the Aurora-A kinase AIR-1 are both required for removal of NPP-3 from the NE. In the images above, NPP-3 (right column, red in merged) is localized on the NE and is removed as mitosis progresses. NPP-3 removal begins near centrosomes (microtubules in green).
Hachet V, Busso C, Toya M, Sugimoto A, Askjaer P, & Gönczy P (2012). The nucleoporin Nup205/NPP-3 is lost near centrosomes at mitotic onset and can modulate the timing of this process in Caenorhabditis elegans embryos. Molecular biology of the cell, 23 (16), 3111-21 PMID: 22740626