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. Author manuscript; available in PMC: 2015 Mar 31.
Published in final edited form as: Nat Cell Biol. 2014 Apr 28;16(6):538–549. doi: 10.1038/ncb2952

Figure 5.

Figure 5

Cyclin B2 and p53 antagonistically control aurora-A-mediated centrosome separation. (a) WT, WT SV40 large T antigen-transformed and p53−/− MEFs transduced with cyclin B2 sh RNA or non-targeting shR NA negative control lentiviruses and analysed for G2 cells with unseparated centrosomes (< 1μm). (b) Images of prophases immunosta ined for p-aurora and γ-tubu lin. (c) Quantification of p-aurora signa I at centrosomes in prophase. (d) Incidence of spindle geometry abnormalities. (e) Images of G2 cells immunostained for p-Plk1T210, γ-tubulin and pH3S10. (f) Quantification of p-Plk1T210 signal at centrosomes in G2 cells. (g) Quantitation of cells with unseparated centrosomes in G2 in the presence or absence of 10nM MLN8054. (h) Incidence of spindle geometry abnormalities in the presence or absence of 10nM MLN8054. (i) Analysis of chromosome segregation errors by live-cell imaging. The analysis was carried out on three independent MEF lines (14-26 cells were analysed per line). (j) Model for antagonistic control of the centrosome splitting signalling cascade by p53 and cyclin B2-Cdk1. In this model, p53 functions to limit the amount of activated (phosphorylated) aurora A by inhibiting AURKA gene transcription and promoting proteosomal degradation of aurora A protein. Cyclin B2-Cdk1, on the other hand, triggers the phosphorylation of the residual aurora A protein pool in a timely manner to induce phosphorylation of centrosome-associated Plk1 and permit centrosome disjunction38,67-70. Whether cyclin B2-Cdk1 triggers aurora A activation directly or indirectly remains to be determined. Colour codes in d and f are as in c. Colour code in h is as in g. DNA in b and e was visualized with Hoechst. Scale bars represent 10 μm. Arrows mark centrosomes. p53−/− cells with supernumerary centrosomes were excluded from the analyses in b-h. Quantifications in a,c,d and f-h were done on three independent MEF lines (per line, 20 cells in a,d,g and h and 10 cells in c and f were analysed). Data represent mean ± s.e.m. Statistical significance was determined by a two-tailed, unpaired t-test. Statistics source data are provided in Supplementary Table 2. *P < 0.05; **P <0.01; ***P <0.001.