The Zn-finger domain of MdmX suppresses cancer progression by promoting genome stability in p53-mutant cells

Ubiquitination controls numerous cellular processes, and its deregulation is associated to many pathologies. The Nse1 subunit in the Smc5/6 complex contains a RING domain with ubiquitin E3 ligase activity and important functions in genome integrity. However, Nse1-dependent ubiquitin targets remain largely unknown. Here, we use label-free quantitative proteomics to analyse the nuclear ubiquitinome of nse1-C274A RING mutant cells. Our results show that Nse1 impacts on the ubiquitination of several proteins involved in DNA damage tolerance, ribosome biogenesis and metabolism that, importantly, extend beyond canonical functions of the Smc5/6 complex in chromosome segregation. In addition, our analysis uncovers an unexpected connection between Nse1 and RNA polymerase I (RNAP I) ubiquitination. Specifically, Nse1 promotes the ubiquitination of K408 and K410 in A190, the largest subunit of RNAP I, to induce its degradation. We propose that this mechanism contributes to Smc5/6-dependent rDNA disjunction in response to transcriptional elongation defects.

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The PHLPP2 phosphatase is a druggable driver of prostate cancer progression

The Journal of Cell Biology ◽

10.1083/jcb.201902048 ◽

2019 ◽

Vol 218 (6) ◽

pp. 1943-1957 ◽

Cited By ~ 12

Author(s):

Dawid G. Nowak ◽

Ksenya Cohen Katsenelson ◽

Kaitlin E. Watrud ◽

Muhan Chen ◽

Grinu Mathew ◽

...

Keyword(s):

Prostate Cancer ◽

Cancer Progression ◽

Metastatic Prostate Cancer ◽

Genetically Engineered ◽

Phosphatase Inhibitors ◽

Genetically Engineered Mouse Model ◽

Key Driver ◽

The Common ◽

Chromosome 16Q ◽

Mutant Cells

Metastatic prostate cancer commonly presents with targeted, bi-allelic mutations of the PTEN and TP53 tumor suppressor genes. In contrast, however, most candidate tumor suppressors are part of large recurrent hemizygous deletions, such as the common chromosome 16q deletion, which involves the AKT-suppressing phosphatase PHLPP2. Using RapidCaP, a genetically engineered mouse model of Pten/Trp53 mutant metastatic prostate cancer, we found that complete loss of Phlpp2 paradoxically blocks prostate tumor growth and disease progression. Surprisingly, we find that Phlpp2 is essential for supporting Myc, a key driver of lethal prostate cancer. Phlpp2 dephosphorylates threonine-58 of Myc, which renders it a limiting positive regulator of Myc stability. Furthermore, we show that small-molecule inhibitors of PHLPP2 can suppress MYC and kill PTEN mutant cells. Our findings reveal that the frequent hemizygous deletions on chromosome 16q present a druggable vulnerability for targeting MYC protein through PHLPP2 phosphatase inhibitors.

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The roles of RNA in DNA double-strand break repair

British Journal of Cancer ◽

10.1038/s41416-019-0624-1 ◽

2020 ◽

Vol 122 (5) ◽

pp. 613-623 ◽

Cited By ~ 20

Author(s):

Aldo S. Bader ◽

Ben R. Hawley ◽

Ania Wilczynska ◽

Martin Bushell

Keyword(s):

Dna Repair ◽

Cancer Progression ◽

Genome Stability ◽

Rna Binding ◽

Rna Binding Proteins ◽

Critical Role ◽

Strand Break ◽

Rna Molecules ◽

Repair Mechanisms ◽

Recent Developments

AbstractEffective DNA repair is essential for cell survival: a failure to correctly repair damage leads to the accumulation of mutations and is the driving force for carcinogenesis. Multiple pathways have evolved to protect against both intrinsic and extrinsic genotoxic events, and recent developments have highlighted an unforeseen critical role for RNA in ensuring genome stability. It is currently unclear exactly how RNA molecules participate in the repair pathways, although many models have been proposed and it is possible that RNA acts in diverse ways to facilitate DNA repair. A number of well-documented DNA repair factors have been described to have RNA-binding capacities and, moreover, screens investigating DNA-damage repair mechanisms have identified RNA-binding proteins as a major group of novel factors involved in DNA repair. In this review, we integrate some of these datasets to identify commonalities that might highlight novel and interesting factors for future investigations. This emerging role for RNA opens up a new dimension in the field of DNA repair; we discuss its impact on our current understanding of DNA repair processes and consider how it might influence cancer progression.

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Hinfp is a guardian of the somatic genome by repressing transposable elements

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2100839118 ◽

2021 ◽

Vol 118 (41) ◽

pp. e2100839118

Author(s):

Niraj K. Nirala ◽

Qi Li ◽

Prachi N. Ghule ◽

Hsi-Ju Chen ◽

Rui Li ◽

...

Keyword(s):

Dna Damage ◽

Transposable Elements ◽

Transposable Element ◽

Cancer Progression ◽

Genome Stability ◽

Genome Instability ◽

Tissue Growth ◽

Loss Of Function ◽

Element Mobilization ◽

Host Genes

Germ cells possess the Piwi-interacting RNA pathway to repress transposable elements and maintain genome stability across generations. Transposable element mobilization in somatic cells does not affect future generations, but nonetheless can lead to pathological outcomes in host tissues. We show here that loss of function of the conserved zinc-finger transcription factor Hinfp causes dysregulation of many host genes and derepression of most transposable elements. There is also substantial DNA damage in somatic tissues of Drosophila after loss of Hinfp. Interference of transposable element mobilization by reverse-transcriptase inhibitors can suppress some of the DNA damage phenotypes. The key cell-autonomous target of Hinfp in this process is Histone1, which encodes linker histones essential for higher-order chromatin assembly. Transgenic expression of Hinfp or Histone1, but not Histone4 of core nucleosome, is sufficient to rescue the defects in repressing transposable elements and host genes. Loss of Hinfp enhances Ras-induced tissue growth and aging-related phenotypes. Therefore, Hinfp is a physiological regulator of Histone1-dependent silencing of most transposable elements, as well as many host genes, and serves as a venue for studying genome instability, cancer progression, neurodegeneration, and aging.

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RB1 Deletion in Retinoblastoma Protein Pathway-Disrupted Cells Results in DNA Damage and Cancer Progression

Molecular and Cellular Biology ◽

10.1128/mcb.00105-19 ◽

2019 ◽

Vol 39 (16) ◽

Cited By ~ 8

Author(s):

Aren E. Marshall ◽

Michael V. Roes ◽

Daniel T. Passos ◽

Megan C. DeWeerd ◽

Andrea C. Chaikovsky ◽

...

Keyword(s):

Dna Damage ◽

Cancer Cells ◽

Cancer Progression ◽

Genome Instability ◽

Retinoblastoma Protein ◽

Rb Pathway ◽

Recombination Repair ◽

Proliferative Control ◽

Immunocompromised Mice ◽

Mutant Cells

ABSTRACT Proliferative control in cancer cells is frequently disrupted by mutations in the retinoblastoma protein (RB) pathway. Intriguingly, RB1 mutations can arise late in tumorigenesis in cancer cells whose RB pathway is already compromised by another mutation. In this study, we present evidence for increased DNA damage and instability in cancer cells with RB pathway defects when RB1 mutations are induced. We generated isogenic RB1 mutant genotypes with CRISPR/Cas9 in a number of cell lines. Cells with even one mutant copy of RB1 have increased basal levels of DNA damage and increased mitotic errors. Elevated levels of reactive oxygen species as well as impaired homologous recombination repair underlie this DNA damage. When xenografted into immunocompromised mice, RB1 mutant cells exhibit an elevated propensity to seed new tumors in recipient lungs. This study offers evidence that late-arising RB1 mutations can facilitate genome instability and cancer progression that are beyond the preexisting proliferative control deficit.

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RB1 deletion in RB-pathway disrupted cells results in DNA damage and cancer progression

10.1101/564567 ◽

2019 ◽

Author(s):

Aren E. Marshall ◽

Michael V. Roes ◽

Daniel T. Passos ◽

Megan C. DeWeerd ◽

Andrea C. Chaikovsky ◽

...

Keyword(s):

Dna Damage ◽

Cancer Cells ◽

Cancer Progression ◽

Genome Instability ◽

Homologous Recombination Repair ◽

Oxygen Species ◽

Rb Pathway ◽

Recombination Repair ◽

Proliferative Control ◽

Mutant Cells

SummaryProliferative control in cancer cells is frequently disrupted by mutations in the RB-pathway. Intriguingly, RB1 mutations can arise late in tumorigenesis in cancer cells whose RB-pathway is already compromised by another mutation. In this study, we present evidence for increased DNA damage and instability in CDKN2A silenced cancer cells when RB1 mutations are induced. We generated isogenic RB1 mutant genotypes with CRISPR in a number of cell lines. Cells with even one mutant copy of RB1 have increased basal levels of DNA damage and increased mitotic errors. Elevated levels of reactive oxygen species as well as impaired homologous recombination repair underlie this DNA damage. When xenografted into immune compromised mice RB1 mutant cells exhibit an elevated propensity to seed new tumors in recipient lungs. This study offers evidence that late arising RB1 mutations can facilitate genome instability and cancer progression that are beyond the pre-existing proliferative control deficit.

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Fanci-FANCD2 Promotes Genome Stability and DNA Repair By Down-Regulating BLM Helicase Activity

Blood ◽

10.1182/blood-2021-152218 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 1113-1113

Author(s):

Fengshan Liang ◽

Arvindhan Nagarajan ◽

Manoj M Pillai ◽

Patrick Sung ◽

Gary M. Kupfer

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Replication Fork ◽

Genome Stability ◽

Head And Neck Tumor ◽

Amino Acid Deletion ◽

Blm Helicase ◽

Dna End Resection ◽

End Resection ◽

Mutant Cells

Abstract Background: Fanconi anemia (FA) is a genetic disease characterized by bone marrow failure, developmental defects, and higher risk of cancer. Mutations in FA genes have been detected commonly in a large swath of cancers. In the FA DNA repair pathway, DNA damage induces the mono-ubiquitination of the FANCI-FANCD2 (ID2) heterodimer and this regulation licenses the execution of downstream DNA damage signaling and repair steps. In response to replication stress, FANCD2 also prevents replication fork collapse during S phase. Bloom syndrome (BS) is also a genomic instability disease, characterized by growth abnormalities and cancer predisposition. The single BS protein, BLM helicase, participates in DNA repair by promoting DNA end resection and double Holliday junction dissolution. It has been shown that BLM is involved in restart of stalled replication fork. FA and BS have functional interactions. In tumor DNA sequencing of the Yale Precision Tumor board, we identified a somatic 6 amino acid deletion in FANCD2 in a head and neck tumor, while a germline point mutation was found on the other allele. We have identified a FANCD2-L822A mutant with defective BLM binding, which was used to further investigate the role of FANCD2-BLM interaction in genome stability and DNA repair. Methods: Highly purified proteins were used to investigate how ID2 affects helicase and DNA end resection activity of the BLM complex. HeLa, FANCD2-deficient, and FANCD2 corrected fibroblast cell lines were used to examine pRPA2 and RAD51 foci formation. We also used DNA fiber assay to detect end resection and isolation of proteins on nascent DNA (iPOND) assay to examine the RAD51 recruitment on replication fork. Results: A somatic 6 amino acid deletion (p819-824) in FANCD2 was identified in a head and neck tumor. FA-D2 mutant cells expressing the mutant cDNA demonstrated defects in FANCD2 mono-ubiquitination and DNA damage hypersensitivity. A FANCD2-L822A mutant with defective BLM binding was identified (Figure A, B). We found that Bloom helicase and its DNA end resection activity within BLM-DNA2-RPA were negatively regulated by the heterodimer ID2 (Figure C, D). Both DNA and BLM binding of the ID2 are required for the inhibitory function. The premature DNA end resection and HU sensitivity in FANCD2 deficient and mutant cells are rescued by BLM knockdown. By iPOND assay, we discovered that FANCD2 antagonizes BLM to promote RAD51 recruitment on HU-stalled replication fork. Conclusions: Our study suggests that the DNA end resection activity of BLM-DNA2 is tightly regulated by FANCD2 to ensure that the nuclease DNA2 normally resects the DNA intermediate needed for efficient DNA repair and RAD51 recruitment to protect replication forks. Our findings highlight that ID2-BLM interaction functions in DNA damage repair to maintain genome stability. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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Defects In DNA Double-Strand Break Repair and Increased Alternative Non-Homologous End Joining Pathways In Multiple Myeloma: Implications For Genome Stability

Blood ◽

10.1182/blood.v122.21.4882.4882 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4882-4882

Author(s):

Ana B Herrero ◽

Jesus F San Miguel ◽

Norma Gutierrez

Keyword(s):

Multiple Myeloma ◽

Cell Lines ◽

Cancer Progression ◽

Genome Stability ◽

Conflicts Of Interest ◽

Genome Instability ◽

Dsb Repair ◽

Nhej Pathway ◽

Slow Kinetics

Abstract Multiple myeloma (MM) is a hematological malignancy characterized by frequent chromosome abnormalities. However, the molecular basis for this genome instability remains unknown. Since DNA rearrangements can be generated thought an improper repair of double strand breaks (DSBs), we investigated the functionality of DSB repair in MM cells. We found that four out of seven MM cell lines analyzed exhibited clear defects in the repair of ionizing radiation (IR)-induced DSBs, revealed by a slow kinetics of g-H2AX disappearance, a prolonged G2/M DNA damage checkpoint activation and an increased sensitivity to IR. An analysis of the proteins that participate in DSB repair revealed no lowered amounts of proteins of the classical NHEJ pathway. However, increased levels of proteins involved in homologous recombination (HR), and in an alternative NHEJ subpathway (Alt-NHEJ) were found in all MM cell lines compared to controls. Interestingly, the Alt-NHEJ protein DNA ligase III was also overexpressed in three out of five samples of plasmatic cells isolated from patients with MM. In vivo assays using a digested plasmid as a substrate revealed slight or non-significant defects in extrachomosomal NHEJ in MM repair-deficient cells, however increased HR was detected by a high percentage of cells with endogenous and IR-induced Rad51 foci. Importantly, the Alt-NHEJ pathway, known to play a role in the generation of deletions and translocations leading to cancer progression, was also found upregulated in MM cells, as revealed by larger deletions and higher sequence microhomology at repair junctions compared to control cells. Taken together, our results uncover aberrant DSB repair in MM. Consequences for genome instability, progression and treatment of the disease will be discussed. Disclosures: No relevant conflicts of interest to declare.

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Telomere Shortening and Its Association with Cell Dysfunction in Lung Diseases

International Journal of Molecular Sciences ◽

10.3390/ijms23010425 ◽

2021 ◽

Vol 23 (1) ◽

pp. 425

Author(s):

Andy Ruiz ◽

Julio Flores-Gonzalez ◽

Ivette Buendia-Roldan ◽

Leslie Chavez-Galan

Keyword(s):

Cancer Progression ◽

Lung Diseases ◽

Genome Stability ◽

Genotoxic Stress ◽

Chronic Obstructive ◽

Telomere Shortening ◽

Obstructive Pulmonary Disease ◽

Cell Dysfunction ◽

Inflammatory Processes ◽

Or Genes

Telomeres are localized at the end of chromosomes to provide genome stability; however, the telomere length tends to be shortened with each cell division inducing a progressive telomere shortening (TS). In addition to age, other factors, such as exposure to pollutants, diet, stress, and disruptions in the shelterin protein complex or genes associated with telomerase induce TS. This phenomenon favors cellular senescence and genotoxic stress, which increases the risk of the development and progression of lung diseases such as idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, SARS-CoV-2 infection, and lung cancer. In an infectious environment, immune cells that exhibit TS are associated with severe lymphopenia and death, whereas in a noninfectious context, naïve T cells that exhibit TS are related to cancer progression and enhanced inflammatory processes. In this review, we discuss how TS modifies the function of the immune system cells, making them inefficient in maintaining homeostasis in the lung. Finally, we discuss the advances in drug and gene therapy for lung diseases where TS could be used as a target for future treatments.

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Opposite Roles for ZEB1 and TMEJ in the Regulation of Breast Cancer Genome Stability

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.727429 ◽

2021 ◽

Vol 9 ◽

Author(s):

Mélanie K. Prodhomme ◽

Sarah Péricart ◽

Roxane M. Pommier ◽

Anne-Pierre Morel ◽

Anne-Cécile Brunac ◽

...

Keyword(s):

Breast Cancer ◽

Dna Repair ◽

Cancer Progression ◽

Genome Stability ◽

Breast Cancer Cells ◽

Epithelial To Mesenchymal Transition ◽

End Joining ◽

Mesenchymal Transition ◽

Repair Genes ◽

Insight Into

Breast cancer cells frequently acquire mutations in faithful DNA repair genes, as exemplified by BRCA-deficiency. Moreover, overexpression of an inaccurate DNA repair pathway may also be at the origin of the genetic instability arising during the course of cancer progression. The specific gain in expression of POLQ, encoding the error-prone DNA polymerase Theta (POLθ) involved in theta-mediated end joining (TMEJ), is associated with a characteristic mutational signature. To gain insight into the mechanistic regulation of POLQ expression, this review briefly presents recent findings on the regulation of POLQ in the claudin-low breast tumor subtype, specifically expressing transcription factors involved in epithelial-to-mesenchymal transition (EMT) such as ZEB1 and displaying a paucity in genomic abnormality.

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