p53 mitotic centrosome localization preserves centrosome integrity and works as sensor for the mitotic surveillance pathway

Abstract

Centrosomal p53 has been described for three decades but its role is still unclear. We previously reported that, in proliferating human cells, p53 transiently moves to centrosomes at each mitosis. Such p53 mitotic centrosome localization (p53-MCL) occurs independently from DNA damage but requires ATM-mediated p53Ser15 phosphorylation (p53Ser15P) on discrete cytoplasmic p53 foci that, through MT dynamics, move to centrosomes during the mitotic spindle formation. Here, we show that inhibition of p53-MCL, obtained by p53 depletion or selective impairment of p53 centrosomal localization, induces centrosome fragmentation in human nontransformed cells. In contrast, tumor cells or mouse cells tolerate p53 depletion, as expected, and p53-MCL inhibition. Such tumor- and species-specific behavior of centrosomal p53 resembles that of the recently identified sensor of centrosome-loss, whose activation triggers the mitotic surveillance pathway in human nontransformed cells but not in tumor cells or mouse cells. The mitotic surveillance pathway prevents the growth of human cells with increased chance of making mitotic errors and accumulating numeral chromosome defects. Thus, we evaluated whether p53-MCL could work as a centrosome-loss sensor and contribute to the activation of the mitotic surveillance pathway. We provide evidence that centrosome-loss triggered by PLK4 inhibition makes p53 orphan of its mitotic dock and promotes accumulation of discrete p53Ser15P foci. These p53 foci are required for the recruitment of 53BP1, a key effector of the mitotic surveillance pathway. Consistently, cells from patients with constitutive impairment of p53-MCL, such as ATM- and PCNT-mutant carriers, accumulate numeral chromosome defects. These findings indicate that, in nontransformed human cells, centrosomal p53 contributes to safeguard genome integrity by working as sensor for the mitotic surveillance pathway.

Moonlighting in Mitosis: Analysis of the Mitotic Functions of Transcription and Splicing Factors

“…Loss of p53 results in centrosome amplification in both human and mouse cells [62][63][64][65][66]. Interestingly, recent work has shown that p53 depletion in human non-transformed cells results in centrosome fragmentation [67]. However, centrosome fragmentation was not observed in p53-deficient mouse cells and human cancer cells, which instead showed centrosome amplification [67], as previously described [65].…”

“…Interestingly, recent work has shown that p53 depletion in human non-transformed cells results in centrosome fragmentation [67]. However, centrosome fragmentation was not observed in p53-deficient mouse cells and human cancer cells, which instead showed centrosome amplification [67], as previously described [65]. Although it has been suggested that p53 might directly contribute to prevention of centrosome amplification [64,65] or fragmentation [67], a compelling evidence for a moonlighting role of p53 at the centrosome is still lacking.…”

DNA Replication Stress and Chromosomal Instability: Dangerous Liaisons

“…It has been reported that the relocalization of p53 from the cytoplasm to mitotic centrosomes occurs only following its phosphorylation by ATM. The authors also showed that inhibition of p53 centrosomal localization, or even acute p53 depletion, led to centrosome fragmentation and, eventually, to cell death, highlighting another mechanism by which genome stability is preserved before the next cell cycle is initiated [73]. Similarly, aside from its role in the replication stress response, ATR has an independent role in preventing CIN in mitosis, as was recently described.…”

Variants of uncertain significance in the era of high-throughput genome sequencing: a lesson from breast and ovary cancers

“…The p53-MCL test takes advantage of the activity of ATM on p53 during mitosis, when ATM phosphorylates p53 at Ser15 and allows its translocation to the centrosomes [82]. This mechanism is important for mitotic surveillance [83] and it has been shown that cells mutated in ATM, such as A-T cells, lack this localization [81]. The p53-MCL test is based on an immunofluorescence assay that analyzes the localization of p53 at the centrosomes in PBMCs during mitosis, which is quantitatively impaired in cells carrying pathogenic ATM mutations [81].…”