Aurora-A inactivation causes mitotic spindle pole fragmentation by unbalancing microtubule-generated forces.
BACKGROUND
Aurora-A is an oncogenic kinase playing well-documented roles in mitotic spindle organisation. We previously found that Aurora-A inactivation yields the formation of spindles with fragmented poles that can drive chromosome mis-segregation. Here we have addressed the mechanism through which Aurora-A activity regulates the structure and cohesion of spindle poles.


RESULTS
We inactivated Aurora-A in human U2OS osteosarcoma cells either by RNA-interference-mediated silencing or treating cultures with the specific inhibitor MLN8237. We show that mitotic spindle pole fragmentation induced by Aurora-A inactivation is associated with microtubule hyperstabilisation. Silencing of the microtubule-stabilising factor ch-TOG prevents spindle pole fragmentation caused by inactivation of Aurora-A alone and concomitantly reduces the hyperstabilisation of microtubules. Furthermore, decreasing pole-directed spindle forces by inhibition of the Eg5 kinesin, or by destabilisation of microtubule-kinetochore attachments, also prevents pole fragmentation in Aurora-A-inactivated mitoses.


CONCLUSIONS
Our findings indicate that microtubule-generated forces are imbalanced in Aurora-A-defective cells and exert abnormal pressure at the level of spindle poles, ultimately causing their fragmentation. This study therefore highlights a novel role of the Aurora-A kinase in regulating the balance between microtubule forces during bipolar spindle assembly.
Institute of Molecular Biology and Pathology, CNR National Research Council, c/o Department of Biology and Biotechnologies, Sapienza University of Rome, Via degli Apuli 4, Rome, Italy.
Italia A
IA
Asteriti
Maria
M
Giubettini
Patrizia
P
Lavia
Giulia
G
Guarguaglini
D064127:Aurora Kinases; D001381:Azepines / Q000494:pharmacology; D006801:Humans; D016547:Kinesins / Q000037:antagonists & inhibitors / Q000378:metabolism; D018386:Kinetochores / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D034622:RNA Interference; D008941:Spindle Apparatus / Q000502:physiology*; D014407:Tumor Cells, Cultured
D001381:Azepines; C470243:KIF11 protein, human; C550258:MLN 8237; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D016547:Kinesins