Inhibiting Crm1 causes the formation of excess acentriolar spindle poles containing NuMA and B23, but does not affect centrosome numbers.
BACKGROUND
B23/nucleophosmin is present on spindle poles at metaphase. Migration of B23 to the poles is under the control of exportin Crm1. B23 at the centrosome plays a role in the control centrosome duplication.


RESULTS
h-Tert-RPE1 cells blocked in prometaphase with low doses of Nocodazol showed a progression to mitosis if Crm1 exportin was inhibited. Under these conditions, the formation of accessory poles containing gamma-tubulin, NuMA (nuclear-mitotic-apparatus) and B23 was induced at metaphase. No effect on centrosome number was observed. In quiescent h-Tert-RPE1 cells, when Crm1 was active, B23 was not detected at the centrosome as well as B23-mutants reported to block centrosome duplication. In addition, the modification of B23 nucleo-cytoplasmic shuttling showed no effect on centrosome duplication.


CONCLUSIONS
Inhibition of Crm1 in early metaphase favours the formation of supplementary acentriolar spindle poles. B23 and NuMA are present at these poles that ultimately focus around the centrosome. Inhibition of Crm1 at metaphase has no effect on the control of centrosome numbers.
Rousselet
Annie
A
UMR144, Institut Curie, 75005 Paris, France. annie.rousselet@espci.fr
D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002460:Cell Line; D018385:Centrosome / Q000737:chemistry* / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D008677:Metaphase; D051379:Mice; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000090243:Nucleophosmin; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D028884:Karyopherins; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C000716967:NPM1 protein, human; C050045:NUMA1 protein, human; C000715570:Npm1 protein, mouse; C489080:Numa1 protein, mouse