In response to DNA replication stress, DNA damage signaling kinases inhibit origin firing and promote the remodeling and stabilization of replication forks, leading to a systemic reduction in DNA synthesis that protects genomic integrity. Little is understood about the regulatory mechanisms of replication stress recovery, including the mechanisms involved in the restart of stalled replication forks. Here, we identify the oncogenic phosphatase PPM1D/WIP1 as a critical regulator of replication fork restart. Upon recovery from replication stress, PPM1D prevents excessive MRE11- and DNA2-dependent nucleolytic degradation of stalled forks. Loss of PPM1D function leads to defects in RAD51 recruitment to chromatin and impairs RAD51-dependent fork restart. Phosphoproteomic analysis reveals that PPM1D regulates a network of ATM substrates, several of which are phosphorylated at an S/T-Q-(E/D)n motif. Strikingly, inhibition of ATM suppresses the deleterious consequences of impaired PPM1D function at replication forks, enabling timely fork restart. The dominant effect of ATM hyper-signaling in suppressing fork restart occurs, in part, through the excessive engagement of 53BP1 and consequent RAD51 antagonization. These findings uncover a new mode of ATM signaling responding to fork stalling and highlights the need for PPM1D to restrain ATM signaling and enable proper fork restart.

• Publikační typ
• časopisecké články MeSH
• preprinty MeSH

The transcription factor p53 is the most frequently impaired tumor suppressor in human cancers. In response to various stress stimuli, p53 activates transcription of genes that mediate its tumor-suppressive functions. Distinctive characteristics of p53 outlined here enable a well-defined program of genes involved in cell cycle arrest, apoptosis, senescence, differentiation, metabolism, autophagy, DNA repair, anti-viral response, and anti-metastatic functions, as well as facilitating autoregulation within the p53 network. This versatile, anti-cancer network governed chiefly by a single protein represents an immense opportunity for targeted cancer treatment, since about half of human tumors retain unmutated p53. During the last two decades, numerous compounds have been developed to block the interaction of p53 with the main negative regulator MDM2. However, small molecule inhibitors of MDM2 only induce a therapeutically desirable apoptotic response in a limited number of cancer types. Moreover, clinical trials of the MDM2 inhibitors as monotherapies have not met expectations and have revealed hematological toxicity as a characteristic adverse effect across this drug class. Currently, combination treatments are the leading strategy for enhancing efficacy and reducing adverse effects of MDM2 inhibitors. This review summarizes efforts to identify and test therapeutics that work synergistically with MDM2 inhibitors. Two main types of drugs have emerged among compounds used in the following combination treatments: first, modulators of the p53-regulated transcriptome (including chromatin modifiers), translatome, and proteome, and second, drugs targeting the downstream pathways such as apoptosis, cell cycle arrest, DNA repair, metabolic stress response, immune response, ferroptosis, and growth factor signaling. Here, we review the current literature in this field, while also highlighting overarching principles that could guide target selection in future combination treatments.

• Klíčová slova
• combination therapy, integrated stress response, nelfinavir, nutlin, p53, polytherapy,
• MeSH
• cílená molekulární terapie * MeSH
• lidé MeSH
• nádorový supresorový protein p53 * metabolismus   genetika   antagonisté a inhibitory   MeSH
• nádory * farmakoterapie   metabolismus   genetika   MeSH
• protinádorové látky * terapeutické užití   farmakologie   MeSH
• protoonkogenní proteiny c-mdm2 antagonisté a inhibitory   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• nádorový supresorový protein p53 * MeSH
• protinádorové látky * MeSH
• protoonkogenní proteiny c-mdm2 MeSH

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
• Názvy látek
• nádorový supresorový protein p53 MeSH
• PPM1D protein, human MeSH Prohlížeč
• proteinfosfatasa 2C * MeSH
• proteinfosfatasy MeSH

• MeSH
• buněčná diferenciace MeSH
• buněčný rodokmen MeSH
• hematopoetické kmenové buňky * cytologie   metabolismus   MeSH
• hematopoéza MeSH
• lidé MeSH
• proteinfosfatasy metabolismus   genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• komentáře MeSH
• úvodníky MeSH
• Názvy látek
• proteinfosfatasy MeSH