PPM1D phosphatase
Dotaz
Zobrazit nápovědu
Oncogene-induced replication stress has been recognized as a major cause of genome instability in cancer cells. Increased expression of cyclin E1 caused by amplification of the CCNE1 gene is a common cause of replication stress in various cancers. Protein phosphatase magnesium-dependent 1 delta (PPM1D) is a negative regulator of p53 and has been implicated in termination of the cell cycle checkpoint. Amplification of the PPM1D gene or frameshift mutations in its final exon promote tumorigenesis. Here, we show that PPM1D activity further increases the replication stress caused by overexpression of cyclin E1. In particular, we demonstrate that cells expressing a truncated mutant of PPM1D progress faster from G1 to S phase and fail to complete licensing of the replication origins. In addition, we show that transcription-replication collisions and replication fork slowing caused by CCNE1 overexpression are exaggerated in cells expressing the truncated PPM1D. Finally, replication speed and accumulation of focal DNA copy number alterations caused by induction of CCNE1 expression was rescued by pharmacological inhibition of PPM1D. We propose that increased activity of PPM1D suppresses the checkpoint function of p53 and thus promotes genome instability in cells expressing the CCNE1 oncogene.
Cell cycle checkpoints, oncogene-induced senescence and programmed cell death represent intrinsic barriers to tumorigenesis. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of the tumour suppressor p53 and has been implicated in termination of the DNA damage response. Here, we addressed the consequences of increased PPM1D activity resulting from the gain-of-function truncating mutations in exon 6 of the PPM1D. We show that while control cells permanently exit the cell cycle and reside in senescence in the presence of DNA damage caused by ionising radiation or replication stress induced by the active RAS oncogene, RPE1-hTERT and BJ-hTERT cells carrying the truncated PPM1D continue proliferation in the presence of DNA damage, form micronuclei and accumulate genomic rearrangements revealed by karyotyping. Further, we show that increased PPM1D activity promotes cell growth in the soft agar and formation of tumours in xenograft models. Finally, expression profiling of the transformed clones revealed dysregulation of several oncogenic and tumour suppressor pathways. Our data support the oncogenic potential of PPM1D in the context of exposure to ionising radiation and oncogene-induced replication stress.
- MeSH
- buněčná smrt genetika MeSH
- lidé MeSH
- myši MeSH
- nádorová transformace buněk * genetika MeSH
- nádorový supresorový protein p53 genetika metabolismus MeSH
- poškození DNA * genetika MeSH
- proliferace buněk genetika MeSH
- proteinfosfatasa 2C * genetika metabolismus MeSH
- proteinfosfatasy genetika metabolismus MeSH
- stárnutí buněk * genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Hematopoietic stem cells (HSCs) ensure blood cell production during the life-time of an organism, and to do so they need to balance self-renewal, proliferation, differentiation, and migration in a steady state as well as in response to stress or injury. Importantly, aberrant proliferation of HSCs leads to hematological malignancies, and thus, tight regulation by various tumor suppressor pathways, including p53, is essential. Protein phosphatase magnesium-dependent 1 delta (PPM1D) is a negative regulator of p53 and promotes cell survival upon induction of genotoxic stress. Truncating mutations in the last exon of PPM1D lead to the production of a stable, enzymatically active protein and are commonly associated with clonal hematopoiesis. Using a transgenic mouse model, we demonstrate that truncated PPM1D reduces self-renewal of HSCs in basal conditions but promotes the development of aggressive AML after exposure to ionizing radiation. Inhibition of PPM1D suppressed the colony growth of leukemic stem and progenitor cells carrying the truncated PPM1D, and remarkably, it provided protection against irradiation-induced cell growth. Altogether, we demonstrate that truncated PPM1D affects HSC maintenance, disrupts normal hematopoiesis, and that its inhibition could be beneficial in the context of therapy-induced AML.
- MeSH
- akutní myeloidní leukemie * genetika MeSH
- mutace MeSH
- myši MeSH
- nádorový supresorový protein p53 * genetika MeSH
- poškození DNA MeSH
- proliferace buněk MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Protein phosphatase magnesium-dependent 1 delta (PPM1D) terminates the cell cycle checkpoint by dephosphorylating the tumour suppressor protein p53. By targeting additional substrates at chromatin, PPM1D contributes to the control of DNA damage response and DNA repair. Using proximity biotinylation followed by proteomic analysis, we identified a novel interaction between PPM1D and the shelterin complex that protects telomeric DNA. In addition, confocal microscopy revealed that endogenous PPM1D localises at telomeres. Further, we found that ATR phosphorylated TRF2 at S410 after induction of DNA double strand breaks at telomeres and this modification increased after inhibition or loss of PPM1D. TRF2 phosphorylation stimulated its interaction with TIN2 both in vitro and at telomeres. Conversely, induced expression of PPM1D impaired localisation of TIN2 and TPP1 at telomeres. Finally, recruitment of the DNA repair factor 53BP1 to the telomeric breaks was strongly reduced after inhibition of PPM1D and was rescued by the expression of TRF2-S410A mutant. Our results suggest that TRF2 phosphorylation promotes the association of TIN2 within the shelterin complex and regulates DNA repair at telomeres.
Upon exposure to genotoxic stress, cells activate DNA damage response (DDR) that coordinates DNA repair with a temporal arrest in the cell cycle progression. DDR is triggered by activation of ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related protein kinases that phosphorylate multiple targets including tumor suppressor protein tumor suppressor p53 (p53). In addition, DNA damage can activate parallel stress response pathways [such as mitogen-activated protein kinase p38 alpha (p38)/MAPK-activated protein kinase 2 (MK2) kinases] contributing to establishing the cell cycle arrest. Wild-type p53-induced phosphatase 1 (WIP1) controls timely inactivation of DDR and is needed for recovery from the G2 checkpoint by counteracting the function of p53. Here, we developed a simple in vitro assay for testing WIP1 substrates in nuclear extracts. Whereas we did not detect any activity of WIP1 toward p38/MK2, we confirmed p53 as a substrate of WIP1. Inhibition or inactivation of WIP1 in U2OS cells increased phosphorylation of p53 at S15 and potentiated its acetylation at K382. Further, we identified Deleted in breast cancer gene 1 (DBC1) as a new substrate of WIP1 but surprisingly, depletion of DBC1 did not interfere with the ability of WIP1 to regulate p53 acetylation. Instead, we have found that WIP1 activity suppresses p53-K382 acetylation by inhibiting the interaction between p53 and the acetyltransferase p300. Newly established phosphatase assay allows an easy comparison of WIP1 ability to dephosphorylate various proteins and thus contributes to identification of its physiological substrates.
- MeSH
- acetylace MeSH
- adaptorové proteiny signální transdukční genetika metabolismus MeSH
- biotest metody MeSH
- buněčné jádro genetika metabolismus MeSH
- fosforylace MeSH
- interakční proteinové domény a motivy MeSH
- lidé MeSH
- nádorové buňky kultivované MeSH
- nádorový supresorový protein p53 genetika metabolismus MeSH
- nádory kostí genetika metabolismus patologie MeSH
- oprava DNA MeSH
- osteosarkom genetika metabolismus patologie MeSH
- poškození DNA MeSH
- proteinfosfatasa 2C genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- dospělí MeSH
- genetické testování metody MeSH
- lidé MeSH
- mentální retardace genetika patologie MeSH
- neurovývojové poruchy * genetika MeSH
- novorozenec MeSH
- proteinfosfatasa 2C genetika MeSH
- výsledek terapie MeSH
- vývojové poruchy u dětí genetika patofyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- novorozenec MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
Genome integrity is protected by the cell-cycle checkpoints that prevent cell proliferation in the presence of DNA damage and allow time for DNA repair. The transient checkpoint arrest together with cellular senescence represent an intrinsic barrier to tumorigenesis. Tumor suppressor p53 is an integral part of the checkpoints and its inactivating mutations promote cancer growth. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of p53. Although its loss impairs recovery from the G2 checkpoint and promotes induction of senescence, amplification of the PPM1D locus or gain-of-function truncating mutations of PPM1D occur in various cancers. Here we used a transgenic mouse model carrying a truncating mutation in exon 6 of PPM1D (Ppm1dT). As with human cell lines, we found that the truncated PPM1D was present at high levels in the mouse thymus. Truncated PPM1D did not affect differentiation of T-cells in the thymus but it impaired their response to ionizing radiation (IR). Thymocytes in Ppm1dT/+ mice did not arrest in the checkpoint and continued to proliferate despite the presence of DNA damage. In addition, we observed a decreased level of apoptosis in the thymi of Ppm1dT/+ mice. Moreover, the frequency of the IR-induced T-cell lymphomas increased in Ppm1dT/+Trp53+/- mice resulting in decreased survival. We conclude that truncated PPM1D partially suppresses the p53 pathway in the mouse thymus and potentiates tumor formation under the condition of a partial loss of p53 function.
- MeSH
- apoptóza * MeSH
- buněčný cyklus MeSH
- ionizující záření MeSH
- lymfom metabolismus MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- nádorový supresorový protein p53 metabolismus MeSH
- nádory vyvolané zářením metabolismus MeSH
- oprava DNA MeSH
- poškození DNA MeSH
- proliferace buněk MeSH
- proteinfosfatasa 2C fyziologie MeSH
- thymocyty cytologie metabolismus MeSH
- thymus * cytologie metabolismus MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Protein phosphatase magnesium-dependent 1 delta (PPM1D) terminates cell response to genotoxic stress by negatively regulating the tumor suppressor p53 and other targets at chromatin. Mutations in the exon 6 of the PPM1D result in production of a highly stable, C-terminally truncated PPM1D. These gain-of-function PPM1D mutations are present in various human cancers but their role in tumorigenesis remains unresolved. Here we show that truncated PPM1D impairs activation of the cell cycle checkpoints in human non-transformed RPE cells and allows proliferation in the presence of DNA damage. Next, we developed a mouse model by introducing a truncating mutation in the PPM1D locus and tested contribution of the oncogenic PPM1DT allele to colon tumorigenesis. We found that p53 pathway was suppressed in colon stem cells harboring PPM1DT resulting in proliferation advantage under genotoxic stress condition. In addition, truncated PPM1D promoted tumor growth in the colon in Apcmin mice and diminished survival. Moreover, tumor organoids derived from colon of the ApcminPpm1dT/+ mice were less sensitive to 5-fluorouracil when compared to ApcminPpm1d+/+and the sensitivity to 5-fluorouracil was restored by inhibition of PPM1D. Finally, we screened colorectal cancer patients and identified recurrent somatic PPM1D mutations in a fraction of colon adenocarcinomas that are p53 proficient and show defects in mismatch DNA repair. In summary, we provide the first in vivo evidence that truncated PPM1D can promote tumor growth and modulate sensitivity to chemotherapy.
- MeSH
- chromatin účinky léků MeSH
- exony genetika MeSH
- fluoruracil farmakologie MeSH
- karcinogeneze účinky léků MeSH
- kontrolní body buněčného cyklu genetika MeSH
- lidé MeSH
- mutace genetika MeSH
- myši MeSH
- nádorový supresorový protein p53 genetika MeSH
- nádory tračníku farmakoterapie genetika patologie MeSH
- oprava DNA účinky léků MeSH
- poškození DNA účinky léků MeSH
- proliferace buněk účinky léků MeSH
- protein familiární adenomatózní polypózy genetika MeSH
- proteinfosfatasa 2C genetika MeSH
- regulace genové exprese u nádorů účinky léků MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Genotoxic stress triggers a combined action of DNA repair and cell cycle checkpoint pathways. Protein phosphatase 2C delta (referred to as WIP1) is involved in timely inactivation of DNA damage response by suppressing function of p53 and other targets at chromatin. Here we show that WIP1 promotes DNA repair through homologous recombination. Loss or inhibition of WIP1 delayed disappearance of the ionizing radiation-induced 53BP1 foci in S/G2 cells and promoted cell death. We identify breast cancer associated protein 1 (BRCA1) as interactor and substrate of WIP1 and demonstrate that WIP1 activity is needed for correct dynamics of BRCA1 recruitment to chromatin flanking the DNA lesion. In addition, WIP1 dephosphorylates 53BP1 at Threonine 543 that was previously implicated in mediating interaction with RIF1. Finally, we report that inhibition of WIP1 allowed accumulation of DNA damage in S/G2 cells and increased sensitivity of cancer cells to a poly-(ADP-ribose) polymerase inhibitor olaparib. We propose that inhibition of WIP1 may increase sensitivity of BRCA1-proficient cancer cells to olaparib.
- MeSH
- 53BP1 metabolismus MeSH
- apoptóza účinky léků MeSH
- chemorezistence účinky léků MeSH
- chromatin metabolismus MeSH
- ftalaziny farmakologie MeSH
- HEK293 buňky MeSH
- homologní rekombinace genetika MeSH
- kontrolní body fáze G2 buněčného cyklu MeSH
- kontrolní body fáze S buněčného cyklu MeSH
- lidé MeSH
- nádorové buněčné linie MeSH
- nádory prsu metabolismus MeSH
- oprava DNA genetika fyziologie MeSH
- PARP inhibitory farmakologie MeSH
- piperaziny farmakologie MeSH
- poškození DNA genetika fyziologie MeSH
- proliferace buněk účinky léků MeSH
- protein BRCA1 metabolismus MeSH
- proteinfosfatasa 2C antagonisté a inhibitory genetika metabolismus MeSH
- protinádorové látky farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
