A cancer-associated, genome protective programme engaging PKCε

Parker, Peter J.; Lockwood, Nicola; Davis, Khalil; Kelly, Joanna R.; Soliman, Tanya; Lopez-Pardo, Ainara; Marshall, J.; Redmond, Joanna M.; Vitale, Marco; Martini, Silvia

doi:10.1016/j.jbior.2020.100759

Cited by 8 publications

(6 citation statements)

References 65 publications

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“…We have previously identified three PKCε-regulated events that provide genome protection in cell lines with a compromised Topo2a-dependent G2 arrest ( 3 ). As p53 and p21 are essential for the Topo2a-dependent G2 arrest in normal, diploid cells, we tested whether experimental loss of p53 resulted in a dependence on PKCε for faithful chromosome segregation in RPE1 cells.…”

Section: Resultsmentioning

confidence: 99%

“…The Topo2a-dependent G2 arrest is a poorly understood control mechanism that is defective in numerous tumour-derived cell lines ( 1 , 2 ). This arrest mechanism is triggered by Topo2 inhibitors such as ICRF193 and if compromised triggers emergent dependence on PKCε failsafe pathways, wherein loss or inhibition of PKCε drives division failure ( 3 ).…”

Section: Introductionmentioning

confidence: 99%

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Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells

et al. 2022

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Topoisomerase 2a (Topo2a)-dependent G2 arrest engenders faithful segregation of sister chromatids, yet in certain tumor cell lines where this arrest is dysfunctional, a PKCε-dependent failsafe pathway can be triggered. Here we elaborate on recent advances in understanding the underlying mechanisms associated with this G2 arrest by determining that p53–p21 signaling is essential for efficient arrest in cell lines, in patient-derived cells, and in colorectal cancer organoids. Regulation of this p53 axis required the SMC5/6 complex, which is distinct from the p53 pathways observed in the DNA damage response. Topo2a inhibition specifically during S phase did not trigger G2 arrest despite affecting completion of DNA replication. Moreover, in cancer cells reliant upon the alternative lengthening of telomeres (ALT) mechanism, a distinct form of Topo2a-dependent, p53-independent G2 arrest was found to be mediated by BLM and Chk1. Importantly, the previously described PKCε-dependent mitotic failsafe was engaged in hTERT-positive cells when Topo2a-dependent G2 arrest was dysfunctional and where p53 was absent, but not in cells dependent on the ALT mechanism. In PKCε knockout mice, p53 deletion elicited tumors were less aggressive than in PKCε-replete animals and exhibited a distinct pattern of chromosomal rearrangements. This evidence suggests the potential of exploiting synthetic lethality in arrest-defective hTERT-positive tumors through PKCε-directed therapeutic intervention. Significance: The identification of a requirement for p53 in stringent Topo2a-dependent G2 arrest and engagement of PKCε failsafe pathways in arrest-defective hTERT-positive cells provides a therapeutic opportunity to induce selective synthetic lethality.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells

et al. 2022

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“…rotective measures are engaged extensively during cell cycle progression to ensure the integrity of genome duplication and the fidelity of the ensuing daughter cells genetic inheritance. A significant role has emerged recently for PKCε in controlling protection from chromosome nondisjunction and successful cell division 1,2 , specifically in a subset of transformed cells that fail to arrest in G2 phase in response to the Topoisomerase 2 (Topo2) inhibitor ICRF-193 3 . Studies to date indicate that PKCε exerts this role in genome protection by directly phosphorylating and switching the specificity of Aurora B 4,5 .…”

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confidence: 99%

A genetically-encoded crosslinker screen identifies SERBP1 as a PKCε substrate influencing translation and cell division

et al. 2021

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The PKCε-regulated genome protective pathway provides transformed cells a failsafe to successfully complete mitosis. Despite the necessary role for Aurora B in this programme, it is unclear whether its requirement is sufficient or if other PKCε cell cycle targets are involved. To address this, we developed a trapping strategy using UV-photocrosslinkable amino acids encoded in the PKCε kinase domain. The validation of the mRNA binding protein SERBP1 as a PKCε substrate revealed a series of mitotic events controlled by the catalytic form of PKCε. PKCε represses protein translation, altering SERBP1 binding to the 40 S ribosomal subunit and promoting the assembly of ribonucleoprotein granules containing SERBP1, termed M-bodies. Independent of Aurora B, SERBP1 is shown to be necessary for chromosome segregation and successful cell division, correlating with M-body formation. This requirement for SERBP1 demonstrates that Aurora B acts in concert with translational regulation in the PKCε-controlled pathway exerting genome protection.

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“…In contrast, the behaviour investigated here relates to the engagement of PKCε in a failsafe programme and unlike the oncogenic driver behaviour, this is in effect protective of properties of a subset of oncogenic states (determined experimentally by the activity/inactivity of the Topo2-dependent G2 arrest [ 21 ]). Inhibition of PKCε in this context is not a direct attack on the drivers of disease but instead targets a tumour-specific vulnerability, resulting in a synthetic lethal outcome, as a function of the G2 arrest competence (discussed [ 52 ]). The apparent normality of the PKCε knockout mouse [ 53 , 54 ], suggests that PKCε intervention in the right context would afford an excellent therapeutic index.…”

Section: Discussionmentioning

confidence: 99%

Co-ordinated control of the Aurora B abscission checkpoint by PKCε complex assembly, midbody recruitment and retention

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Soliman

Davis

et al. 2021

Biochemical Journal

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A requirement for PKCε in exiting from the Aurora B dependent abscission checkpoint is associated with events at the midbody, however, the recruitment, retention and action of PKCε in this compartment are poorly understood. Here, the prerequisite for 14-3-3 complex assembly in this pathway is directly linked to the phosphorylation of Aurora B S227 at the midbody. However, while essential for PKCε control of Aurora B, 14-3-3 association is shown to be unnecessary for the activity-dependent enrichment of PKCε at the midbody. This localisation is demonstrated to be an autonomous property of the inactive PKCε D532N mutant, consistent with activity-dependent dissociation. The C1A and C1B domains are necessary for this localisation, while the C2 domain and inter-C1 domain (IC1D) are necessary for retention at the midbody. Furthermore, it is shown that while the IC1D mutant retains 14-3-3 complex proficiency, it does not support Aurora B phosphorylation, nor rescues division failure observed with knockdown of endogenous PKCε. It is concluded that the concerted action of multiple independent events facilitates PKCε phosphorylation of Aurora B at the midbody to control exit from the abscission checkpoint.

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A cancer-associated, genome protective programme engaging PKCε

Cited by 8 publications

References 65 publications

Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells

Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells

A genetically-encoded crosslinker screen identifies SERBP1 as a PKCε substrate influencing translation and cell division

Co-ordinated control of the Aurora B abscission checkpoint by PKCε complex assembly, midbody recruitment and retention

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