Nuclear Membrane Mechanics

In the fission yeast Schizosaccharomyces pombe, the nucleus is tethered to the cytoskeleton by KASH domain-containing proteins in the outer nuclear membrane and SUN domain-containing proteins in the inner nuclear membrane. By exerting force on these SUN-KASH complexes, the cytoskeleton controls the position of the nucleus within the cell. Centromeric DNA inside the nucleus has been observed to cluster near SUN-KASH complexes during interphase, raising the possibility that this association mediates a functional connection to the cytoskeleton. King et al. have identified an inner nuclear membrane protein (Ima1) in S. pombe that links DNA to SUN-KASH complexes. They show that Ima1 binds to centromeric DNA in vitro and colocalizes with the SUN domain-containing protein Sad1 at the inner nuclear membrane; in Ima1-deficient yeast, colocalization between centromeric DNA and Sad1 was disrupted, and nuclei were frequently deformed and asymmetric. The authors propose that these protein-protein interactions may therefore be required to maintain nuclear shape and integrity in the face of cytoplasmic tensioners and provide a means by which cytoskeletal forces contribute to organizing DNA within the nucleus

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Cell 134, 427 (2008)