• Cancer chemotherapy
• DNA repair
• Drug resistance
• Interstrand crosslink
• Unhooking

• Humans
• DNA Repair
• DNA Adducts/metabolism
• DNA/metabolism
• DNA Damage
• Animals
• Cross-Linking Reagents
• Neoplasms/genetics
• Neoplasms/drug therapy
• Neoplasms/metabolism
• DNA Replication

• Z01 AG000746 Intramural NIH HHS

• CML progression
• DNA repair
• FANCD2
• chronic myeloid leukemia
• genomic instability
• poor survival

• 14-Med-2817-02. KACST

• DNA interstrand crosslink
• DNA repair
• cancer
• genome instability
• neurodegeneration

• Animals
• Humans
• Cross-Linking Reagents/chemistry
• DNA Damage
• DNA Repair
• DNA Replication
• Genomic Instability
• Homeostasis
• Drug Therapy

• P01 CA174653 NCI NIH HHS
• R35 CA197606 NCI NIH HHS

• Fanconi anemia
• PCNA monoubiquitination
• interstrand crosslink
• mismatch repair
• replication stress

• The Dutch Cancer Society
• Dutch Ministry of Health, Welfare and Sport

• Fanconi anemia
• colorectal cancer
• predictive biomarker
• prognostic biomarker
• synthetic lethality
• target therapy

• CAG instability
• DNA repair
• FAN1
• FAN1 nuclease activity
• GWAS
• Huntington’s disease
• MLH1
• MSH3
• mismatch repair
• repeat expansion

• Animals
• Binding, Competitive
• Brain/enzymology
• Brain/pathology
• Cell Line, Tumor
• DNA Damage
• DNA Mismatch Repair
• Endodeoxyribonucleases/genetics
• Endodeoxyribonucleases/metabolism
• Exodeoxyribonucleases/genetics
• Exodeoxyribonucleases/metabolism
• HEK293 Cells
• Humans
• Huntingtin Protein/genetics
• Huntingtin Protein/metabolism
• Huntington Disease/enzymology
• Huntington Disease/genetics
• Huntington Disease/pathology
• Mice
• Multifunctional Enzymes/genetics
• Multifunctional Enzymes/metabolism
• MutL Protein Homolog 1/genetics
• MutL Protein Homolog 1/metabolism
• MutS Homolog 3 Protein/genetics
• MutS Homolog 3 Protein/metabolism
• Protein Binding
• Protein Interaction Domains and Motifs
• Trinucleotide Repeat Expansion

• Wellcome Trust
• MR/L023784/2 Medical Research Council
• 200181/Z/15/Z Wellcome Trust

During S phase, the cooperation between the macromolecular complexes regulating DNA synthesis, epigenetic information maintenance and DNA repair is advantageous for cells, as they can rapidly detect DNA damage and initiate the DNA damage response (DDR). UHRF1 is a fundamental epigenetic regulator; its ability to coordinate DNA methylation and histone code is unique across proteomes of different species. Recently, UHRF1’s role in DNA damage repair has been explored and recognized to be as important as its role in maintaining the epigenome. UHRF1 is a sensor for interstrand crosslinks and a determinant for the switch towards homologous recombination in the repair of double-strand breaks; its loss results in enhanced sensitivity to DNA damage. These functions are finely regulated by specific post-translational modifications and are mediated by the SRA domain, which binds to damaged DNA, and the RING domain. Here, we review recent studies on the role of UHRF1 in DDR focusing on how it recognizes DNA damage and cooperates with other proteins in its repair. We then discuss how UHRF1’s epigenetic abilities in reading and writing histone modifications, or its interactions with ncRNAs, could interlace with its role in DDR.

• BACH1/BRIP1
• Chl1p
• Chromatin remodeling
• genomic stability
• tumorigenesis

• BRCA mutation
• Gorlin syndrome
• Hereditary ovarian cancer
• Lynch syndrome
• Peutz-Jeghers syndrome

• Carcinoma, Ovarian Epithelial
• Female
• Genetic Predisposition to Disease
• Humans
• Molecular Biology
• Ovarian Neoplasms/diagnostic imaging
• Ovarian Neoplasms/genetics
• Ovarian Neoplasms/therapy
• Radiologists

• DNA interstrand cross-link
• FANCD2
• Fanconi anemia
• ICL
• NEIL3
• traverse

• DNA damage response
• DNA repair
• MUS81
• SMX nuclease
• XPF
• crosslinks
• recombination
• telomeres

• Animals
• DNA Damage
• DNA Repair
• Genomic Instability
• Humans
• MutS Homolog 3 Protein/genetics
• MutS Homolog 3 Protein/metabolism
• Neoplasms/genetics
• Neoplasms/metabolism
• Protein Interaction Maps
• Recombinases/genetics
• Recombinases/metabolism

• 11582 Cancer Research UK
• FC001212 Cancer Research UK
• Wellcome Trust
• FC001212 Wellcome Trust
• FC001212 Medical Research Council

• DNA repair
• E2-conjugating enzymes (E2s)
• cell cycle
• genome stability
• telomeres
• ubiquitin and ubiquitin-like proteins (UBLs)

• Genomic Instability
• Humans
• Protein Processing, Post-Translational
• Ubiquitin/genetics
• Ubiquitin/metabolism
• Ubiquitin-Conjugating Enzymes/metabolism
• Ubiquitins/metabolism

• DNA repair
• FAN1
• Huntington’s disease
• karyomegalic interstitial nephritis
• modifier
• nuclease
• repeat instability

• Animals
• DNA Repair/genetics
• Endodeoxyribonucleases/genetics
• Exodeoxyribonucleases/genetics
• Genes, Modifier/genetics
• Genomic Instability/genetics
• Humans
• Huntington Disease/genetics
• Multifunctional Enzymes/genetics
• Spinocerebellar Ataxias/genetics
• Trinucleotide Repeat Expansion/genetics

• FRN148910 CIHR
• FDN-388879 CIHR

Fanconi anemia (FA) is a hereditary chromosomal instability disorder often displaying congenital abnormalities and characterized by a predisposition to progressive bone marrow failure (BMF) and cancer. Over the last 25 years since the discovery of the first linkage of genetic mutations to FA, its molecular genetic landscape has expanded tremendously as it became apparent that FA is a disease characterized by a defect in a specific DNA repair pathway responsible for the correction of covalent cross-links between the two complementary strands of the DNA double helix. This pathway has become increasingly complex, with the discovery of now over 20 FA-linked genes implicated in interstrand cross-link (ICL) repair. Moreover, gene products known to be involved in double-strand break (DSB) repair, mismatch repair (MMR), and nucleotide excision repair (NER) play roles in the ICL response and repair of associated DNA damage. While ICL repair is predominantly coupled with DNA replication, it also can occur in non-replicating cells. DNA damage accumulation and hematopoietic stem cell failure are thought to contribute to the increased inflammation and oxidative stress prevalent in FA. Adding to its confounding nature, certain FA gene products are also engaged in the response to replication stress, caused endogenously or by agents other than ICL-inducing drugs. In this review, we discuss the mechanistic aspects of the FA pathway and the molecular defects leading to elevated replication stress believed to underlie the cellular phenotypes and clinical features of FA.

• DNA repair
• DNA replication
• Fanconi anemia
• cancer
• chromosome
• genetic diseases
• genomic instability
• helicase

• Animals
• DNA Damage
• DNA Replication
• Fanconi Anemia/genetics
• Fanconi Anemia/metabolism
• Fanconi Anemia Complementation Group Proteins/genetics
• Fanconi Anemia Complementation Group Proteins/metabolism
• Genomic Instability
• Humans
• Stress, Physiological

• 1ZIAAG000753-09 NIA NIH HHS

• DNA polymerase
• DNA replication
• Genomic stability
• MMR
• Microsatellite instability
• Mutagenesis

• BACH1
• BRIP1
• Fanconi anemia
• Gametogenesis
• MLH1
• Meiotic prophase I

• DNA repair
• FANCJ helicase
• Fanconi Anemia
• MSH2
• crosslink repair
• mismatch repair

• DNA interstrand cross-link
• DNA repair
• Fanconi anemia
• cancer therapeutics
• ubiquitin signaling

• Animals
• Antineoplastic Agents/therapeutic use
• DNA Damage
• DNA Repair
• Fanconi Anemia/metabolism
• Humans
• Neoplasms/metabolism
• Neoplasms/therapy
• Signal Transduction

• Cell cycle
• Chromatin remodeling genes
• DNA repair genes

Several proteins in the BRCA-Fanconi anemia (FA) pathway, such as FANCJ, BRCA1, and FANCD2, interact with mismatch repair (MMR) pathway factors, but the significance of this link remains unknown. Unlike the BRCA-FA pathway, the MMR pathway is not essential for cells to survive toxic DNA interstrand crosslinks (ICLs), although MMR proteins bind ICLs and other DNA structures that form at stalled replication forks. We hypothesized that MMR proteins corrupt ICL repair in cells that lack crosstalk between BRCA-FA and MMR pathways. Here, we show that ICL sensitivity of cells lacking the interaction between FANCJ and the MMR protein MLH1 is suppressed by depletion of the upstream mismatch recognition factor MSH2. MSH2 depletion suppresses an aberrant DNA damage response, restores cell cycle progression, and promotes ICL resistance through a Rad18-dependent mechanism. MSH2 depletion also suppresses ICL sensitivity in cells deficient for BRCA1 or FANCD2, but not FANCA. Rescue by Msh2 loss was confirmed in Fancd2-null primary mouse cells. Thus, we propose that regulation of MSH2-dependent DNA damage response underlies the importance of interactions between BRCA-FA and MMR pathways.

• FANCJ
• Fanconi anemia
• MLH1
• mismatch repair
• replication stress

Fanca contributes to both somatic hypermutation and class switch recombination events in splenic B cells.

Fanconi anemia is a rare genetic disorder that can lead to bone marrow failure, congenital abnormalities, and increased risk for leukemia and cancer. Cells with loss-of-function mutations in the FANC pathway are characterized by chromosome fragility, altered mutability, and abnormal regulation of the nonhomologous end-joining (NHEJ) pathway. Somatic hypermutation (SHM) and immunoglobulin (Ig) class switch recombination (CSR) enable B cells to produce high-affinity antibodies of various isotypes. Both processes are initiated after the generation of dG:dU mismatches by activation-induced cytidine deaminase. Whereas SHM involves an error-prone repair process that introduces novel point mutations into the Ig gene, the mismatches generated during CSR are processed to create double-stranded breaks (DSBs) in DNA, which are then repaired by the NHEJ pathway. As several lines of evidence suggest a possible role for the FANC pathway in SHM and CSR, we analyzed both processes in B cells derived from Fanca^−/− mice. Here we show that Fanca is required for the induction of transition mutations at A/T residues during SHM and that despite globally normal CSR function in splenic B cells, Fanca is required during CSR to stabilize duplexes between pairs of short microhomology regions, thereby impeding short-range recombination downstream of DSB formation.

• DNA repair
• Fanconi anemia
• bone marrow failure

Translesion DNA synthesis (TLS) can use specialized DNA polymerases to insert and/or extend nucleotides across lesions, thereby limiting stalled replication fork collapse and the potential for cell death. Recent studies have shown that monoubiquitinated proliferating cell nuclear antigen (PCNA) plays an important role in recruitment of Y-family TLS polymerases to stalled replication forks after DNA damage treatment. To explore the possible roles of other factors that regulate the ultraviolet (UV)-induced assembly of specialized DNA polymerases at arrested replication forks, we performed immunoprecipitation experiments combined with mass spectrometry and established that DNA polymerase kappa (Polκ) can partner with MSH2, an important mismatch repair protein associated with hereditary non-polyposis colorectal cancer. We found that depletion of MSH2 impairs PCNA monoubiquitination and the formation of foci containing Polκ and other TLS polymerases after UV irradiation of cells. Interestingly, expression of MSH2 in Rad18-deficient cells increased UV-induced Polκ and REV1 focus formation without detectable changes in PCNA monoubiquitination, indicating that MSH2 can regulate post-UV focus formation by specialized DNA polymerases in both PCNA monoubiquitination-dependent and -independent fashions. Moreover, we observed that MSH2 can facilitate TLS across cyclobutane pyrimidine dimers photoproducts in living cells, presenting a novel role of MSH2 in post-UV cellular responses.

• Animals
• Antineoplastic Agents/adverse effects
• Cell Cycle
• Cross-Linking Reagents/adverse effects
• Cross-Linking Reagents/toxicity
• DNA Damage
• DNA Repair
• DNA Repair Enzymes/metabolism
• Humans
• Models, Biological
• Recombinational DNA Repair
• S Phase

• R01 CA092245 NCI NIH HHS
• R01 CA167826 NCI NIH HHS
• CA167826 NCI NIH HHS
• CA92245 NCI NIH HHS

• Animals
• DNA Damage
• DNA Mismatch Repair
• DNA-Binding Proteins/genetics
• DNA-Binding Proteins/metabolism
• Humans
• MutS Homolog 2 Protein/genetics
• MutS Homolog 2 Protein/metabolism
• Signal Transduction

• R01 CA106575 NCI NIH HHS
• CA106575 NCI NIH HHS

Interstrand crosslinks covalently link complementary DNA strands, block replication and transcription, and can trigger cell death. In eukaryotic systems several pathways, including the Fanconi Anemia pathway, are involved in repairing interstrand crosslinks, but their precise mechanisms remain enigmatic. The lack of functional homologs in simpler model organisms has significantly hampered progress in this field. Two recent studies have finally identified a Fanconi-like interstrand crosslink repair pathway in yeast. Future studies in this simplistic model organism promise to greatly improve our basic understanding of complex interstrand crosslink repair pathways like the Fanconi pathway.

Fanconi anemia (FA) is a devastating genetic disease, associated with genomic instability and defects in DNA interstrand cross-link (ICL) repair. The FA repair pathway is not thought to be conserved in budding yeast, and although the yeast Mph1 helicase is a putative homolog of human FANCM, yeast cells disrupted for MPH1 are not sensitive to ICLs. Here, we reveal a key role for Mph1 in ICL repair when the Pso2 exonuclease is inactivated. We find that the yeast FANCM ortholog Mph1 physically and functionally interacts with Mgm101, a protein previously implicated in mitochondrial DNA repair, and the MutSα mismatch repair factor (Msh2-Msh6). Co-disruption of MPH1, MGM101, MSH6, or MSH2 with PSO2 produces a lesion-specific increase in ICL sensitivity, the elevation of ICL-induced chromosomal rearrangements, and persistence of ICL-associated DNA double-strand breaks. We find that Mph1-Mgm101-MutSα directs the ICL-induced recruitment of Exo1 to chromatin, and we propose that Exo1 is an alternative 5′-3′ exonuclease utilised for ICL repair in the absence of Pso2. Moreover, ICL-induced Rad51 chromatin loading is delayed when both Pso2 and components of the Mph1-Mgm101-MutSα and Exo1 pathway are inactivated, demonstrating that the homologous recombination stages of ICL repair are inhibited. Finally, the FANCJ- and FANCP-related factors Chl1 and Slx4, respectively, are also components of the genetic pathway controlled by Mph1-Mgm101-MutSα. Together this suggests that a prototypical FA–related ICL repair pathway operates in budding yeast, which acts redundantly with the pathway controlled by Pso2, and is required for the targeting of Exo1 to chromatin to execute ICL repair.

Individuals with Fanconi anemia (FA) suffer from bone marrow failure and from elevated rates of haematological and solid malignancy. Moreover, FA patients exhibit extreme sensitivity to DNA interstrand cross-links (ICLs), but not other forms of DNA damage. Despite recent progress in identifying and characterising FA factors, little is known about the mechanistic basis of the ICL repair defect in FA. The identification and characterisation of FA–like pathways in simple model eukaryotes, amenable to genetic dissection, would clearly accelerate progress. Here, we have identified an ICL repair pathway in budding yeast that has significant similarities to the FA pathway and that acts in parallel to an established pathway controlled by the Pso2 exonuclease. We have discovered that a key component of this pathway, the FANCM-like helicase, Mph1, interacts and collaborates with a mismatch repair factor (MutSα) and a novel nuclear DNA repair factor Mgm101 to control ICL repair. We also found that a central role of these factors is to recruit Exonuclease 1 (Exo1) to ICL-damaged chromatin, and propose that this factor acts redundantly with Pso2 to execute the exonucleolytic processing of ICLs. Our findings reveal new mechanistic insights into the control of ICL repair by FA–like proteins in an important model organism.

• Chromosomal Proteins, Non-Histone/genetics
• Chromosomal Proteins, Non-Histone/metabolism
• DEAD-box RNA Helicases/deficiency
• DEAD-box RNA Helicases/genetics
• DNA Breaks, Double-Stranded
• DNA Repair
• DNA-Binding Proteins/genetics
• DNA-Binding Proteins/metabolism
• Endodeoxyribonucleases/deficiency
• Endodeoxyribonucleases/genetics
• Endodeoxyribonucleases/metabolism
• Exodeoxyribonucleases/genetics
• Exodeoxyribonucleases/metabolism
• Fanconi Anemia/genetics
• Humans
• Mitochondrial Proteins/genetics
• Mitochondrial Proteins/metabolism
• Models, Biological
• MutS Homolog 2 Protein/genetics
• MutS Homolog 2 Protein/metabolism
• Saccharomyces cerevisiae/genetics
• Saccharomyces cerevisiae/metabolism
• Saccharomyces cerevisiae Proteins/genetics
• Saccharomyces cerevisiae Proteins/metabolism
• Signal Transduction/genetics

• CA9047/A10111 Cancer Research UK

Guanine quadruplex (G4 DNA) is a four-stranded structure that contributes to genome instability and site-specific recombination. G4 DNA folds from sequences containing tandemly repetitive guanines, sequence motifs that are found throughout prokaryote and eukaryote genomes. While some cellular activities have been identified with binding or processing G4 DNA, the factors and pathways governing G4 DNA metabolism are largely undefined. Highly conserved mismatch repair factors have emerged as potential G4-responding complexes because, in addition to initiating heteroduplex correction, the human homologs bind non-B form DNA with high affinity. Moreover, the MutS homologs across species have the capacity to recognize a diverse range of DNA pairing variations and damage, suggesting a conserved ability to bind non-B form DNA.

Here, we asked if E. coli MutS and a heteroduplex recognition mutant, MutS F36A, were capable of recognizing and responding to G4 DNA structures. We find by mobility shift assay that E. coli MutS binds to G4 DNA with high affinity better than binding to G-T heteroduplexes. In the same assay, MutS F36A failed to recognize G-T mismatched oligonucleotides, as expected, but retained an ability to bind to G4 DNA. Association with G4 DNA by MutS is not likely to activate the mismatch repair pathway because nucleotide binding did not promote release of MutS or MutS F36A from G4 DNA as it does for heteroduplexes. G4 recognition activities occur under physiological conditions, and we find that M13 phage harboring G4-capable DNA poorly infected a MutS deficient strain of E. coli compared to M13mp18, suggesting functional roles for mismatch repair factors in the cellular response to unstable genomic elements.

Taken together, our findings demonstrate that E. coli MutS has a binding activity specific for non-B form G4 DNA, but such binding appears independent of canonical heteroduplex repair activation.