A mammalian Partner of inscuteable binds NuMA and regulates mitotic spindle organization.
Asymmetric cell division requires the orientation of mitotic spindles along the cell-polarity axis. In Drosophila neuroblasts, this involves the interaction of the proteins Inscuteable (Insc) and Partner of inscuteable (Pins). We report here that a human Pins-related protein, called LGN, is instead essential for the assembly and organization of the mitotic spindle. LGN is cytoplasmic in interphase cells, but associates with the spindle poles during mitosis. Ectopic expression of LGN disrupts spindle-pole organization and chromosome segregation. Silencing of LGN expression by RNA interference also disrupts spindle-pole organization and prevents normal chromosome segregation. We found that LGN binds the nuclear mitotic apparatus protein NuMA, which tethers spindles at the poles, and that this interaction is required for the LGN phenotype. Anti-LGN antibodies and the LGN-binding domain of NuMA both trigger microtubule aster formation in mitotic Xenopus egg extracts, and the NuMA-binding domain of LGN blocks aster assembly in egg extracts treated with taxol. Thus, we have identified a mammalian Pins homologue as a key regulator of spindle organization during mitosis.
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Centre for Cell Signalling and Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA. qd2n@virginia.edu
Stukenberg
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Macara
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D000818:Animals; D000906:Antibodies; D034961:Antigens, Nuclear; D001665:Binding Sites / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D015870:Gene Expression / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D019476:Insect Proteins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000166:cytology; D008322:Mammals; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D012313:RNA / Q000494:pharmacology; D011817:Rabbits; D008941:Spindle Apparatus / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins
D000906:Antibodies; D034961:Antigens, Nuclear; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; C102754:GPSM2 protein, human; D019476:Insect Proteins; D047908:Intracellular Signaling Peptides and Proteins; C489079:NUMA1 protein, Xenopus; C050045:NUMA1 protein, human; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; C405164:Pins protein, Drosophila; D029867:Xenopus Proteins; D012313:RNA