p31comet Induces Cellular Senescence through p21 Accumulation and Mad2 Disruption

Abstract

Functional suppression of spindle checkpoint protein activity results in apoptotic cell death arising from mitotic failure, including defective spindle formation, chromosome missegregation, and premature mitotic exit. The recently identified p31 comet protein acts as a spindle checkpoint silencer via communication with the transient Mad2 complex. In the present study, we found that p31 comet overexpression led to two distinct phenotypic changes, cellular apoptosis and senescence. Because of a paucity of direct molecular link of spindle checkpoint to cellular senescence, however, the present report focuses on the relationship between abnormal spindle checkpoint formation and p31 comet -induced senescence by using susceptible tumor cell lines. p31 comet -induced senescence was accompanied by mitotic catastrophe with massive nuclear and chromosomal abnormalities. The progression of the senescence was completely inhibited by the depletion of p21 Waf1/Cip1 and partly inhibited by the depletion of the tumor suppressor protein p53. Notably, p21 Waf1/Cip1 depletion caused a dramatic phenotypic conversion of p31 comet -induced senescence into cell death through mitotic catastrophe, indicating that p21 Waf1/Cip1 is a major mediator of p31 comet -induced cellular senescence. In contrast to wild-type p31 comet , overexpression of a p31 mutant lacking the Mad2 binding region did not cause senescence. Moreover, depletion of Mad2 by small interfering RNA induced senescence. Here, we show that p31 comet induces tumor cell senescence by mediating p21 Waf1/Cip1 accumulation and Mad2 disruption and that these effects are dependent on a direct interaction of p31 comet with Mad2. Our results could be used to control tumor growth. (Mol Cancer Res 2009;7(3):371 -82)

MAD2 depletion triggers premature cellular senescence in human primary fibroblasts by activating a P53 pathway preventing aneuploid cells propagation

“…These results are consistent with a recent paper showing that p53 depletion permits the accumulation of non-diploid cells, suggesting involvement of p53 in a ''tolerance'' mechanism of aneuploid cells (Thompson and Compton, 2010). Another recent article evidenced a link between Mad2 and p21 WAF1 , in particular Mad2 reduction was associated to p21 WAF1 increase following over-expression of p31 comet , a Mad2 interacting protein, considered a ''silencer'' of the SAC (Yun et al, 2009). Moreover, it was shown that Mad2 overexpression is associated with aneuploidy induced by inactivation of pRb and p53tumor suppressors in tumor cells (Schvartzman et al, 2011).…”

MTBP plays a crucial role in mitotic progression and chromosome segregation

“…The siRNA oligonucleotides were chemically synthesized at Dharmacon RNA Technologies (Lafayette, CO, USA). The sequences for siRNAs used in this study were human Mad2 (5 0 -AAGTGGTGAGGTCCTGGAAAG-3 0 ), 35 human BubR1 (5 0 -AACGGGCAUUUGAAUAUGAAA-3 0 ), 36 human Mad1 (5 0 -AACAGGCA GTGTCAGCAGAAC-3 0 ), 37 and human MTBP#1 (5 0 -GCCACAUUGAUUCACU CAGUU-3 0 ). Human MTBP#2 and control non-target 1 siRNAs were purchased from Santa Cruz Biotechnology and Dharmacon RNA Technologies, respectively.…”

Molecular definitions of cell death subroutines: recommendations of the Nomenclature Committee on Cell Death 2012

“…These include, but are not limited to, the activation of the DNA damage-responsive protease caspase-2, 114 of the tumor suppressor TP53 109,115 and of other members of the TP53 family, including the TP73 variant TAp73. 116,117 In view of recent results from several laboratories indicating that mitotic aberrations can induce cell senescence, [118][119][120] and that cell death can be either apoptotic or necrotic, 8 we have recently proposed a novel definition and categorization of mitotic catastrophe based on purely functional considerations. 108 Thus, mitotic catastrophe would not constitute a 'pure' cell death executioner pathway, but an oncosuppressive mechanism that: (i) is initiated by perturbations of the mitotic apparatus (i.e., chromosomes and the complex Figure 3 Regulated necrosis.…”