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Molecular Cell Feb 2024The Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1, and RMI2 to form the BTR complex, which dissolves double Holliday junctions and DNA...
The Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1, and RMI2 to form the BTR complex, which dissolves double Holliday junctions and DNA replication intermediates to promote sister chromatid disjunction before cell division. In its absence, structure-specific nucleases like the SMX complex (comprising SLX1-SLX4, MUS81-EME1, and XPF-ERCC1) can cleave joint DNA molecules instead, but cells deficient in both BTR and SMX are not viable. Here, we identify a negative genetic interaction between BLM loss and deficiency in the BRCA1-BARD1 tumor suppressor complex. We show that this is due to a previously overlooked role for BARD1 in recruiting SLX4 to resolve DNA intermediates left unprocessed by BLM in the preceding interphase. Consequently, cells with defective BLM and BRCA1-BARD1 accumulate catastrophic levels of chromosome breakage and micronucleation, leading to cell death. Thus, we reveal mechanistic insights into SLX4 recruitment to DNA lesions, with potential clinical implications for treating BRCA1-deficient tumors.
Topics: Humans; DNA; DNA Repair; DNA Replication; DNA, Cruciform; DNA-Binding Proteins; Recombinases; RecQ Helicases
PubMed: 38266639
DOI: 10.1016/j.molcel.2023.12.040 -
Nature Communications Jul 2021Homology-directed repair (HDR), a critical DNA repair pathway in mammalian cells, is complex, leading to multiple outcomes with different impacts on genomic integrity....
Homology-directed repair (HDR), a critical DNA repair pathway in mammalian cells, is complex, leading to multiple outcomes with different impacts on genomic integrity. However, the factors that control these different outcomes are often not well understood. Here we show that SWS1-SWSAP1-SPIDR controls distinct types of HDR. Despite their requirement for stable assembly of RAD51 recombinase at DNA damage sites, these proteins are not essential for intra-chromosomal HDR, providing insight into why patients and mice with mutations are viable. However, SWS1-SWSAP1-SPIDR is critical for inter-homolog HDR, the first mitotic factor identified specifically for this function. Furthermore, SWS1-SWSAP1-SPIDR drives the high level of sister-chromatid exchange, promotes long-range loss of heterozygosity often involved with cancer initiation, and impels the poor growth of BLM helicase-deficient cells. The relevance of these genetic interactions is evident as SWSAP1 loss prolongs Blm-mutant embryo survival, suggesting a possible druggable target for the treatment of Bloom syndrome.
Topics: Animals; Bloom Syndrome; Cell Proliferation; DNA-Binding Proteins; HEK293 Cells; Homologous Recombination; Humans; Meiosis; Mice; Mitosis; Mouse Embryonic Stem Cells; Multiprotein Complexes; Mutation; Phenotype; Rad51 Recombinase; Sister Chromatid Exchange; Survival Analysis
PubMed: 34253720
DOI: 10.1038/s41467-021-24205-6 -
Frontiers in Immunology 2021Type I interferons (IFNs) as part of the innate immune system have an outstanding importance as antiviral defense cytokines that stimulate innate and adaptive immune... (Review)
Review
Type I interferons (IFNs) as part of the innate immune system have an outstanding importance as antiviral defense cytokines that stimulate innate and adaptive immune responses. Upon sensing of pattern recognition particles (PRPs) such as nucleic acids, IFN secretion is activated and induces the expression of interferon stimulated genes (ISGs). Uncontrolled constitutive activation of the type I IFN system can lead to autoinflammation and autoimmunity, which is observed in autoimmune disorders such as systemic lupus erythematodes and in monogenic interferonopathies. They are caused by mutations in genes which are involved in sensing or metabolism of intracellular nucleic acids and DNA repair. Many authors described mechanisms of type I IFN secretion upon increased DNA damage, including the formation of micronuclei, cytosolic chromatin fragments and destabilization of DNA binding proteins. Hereditary cutaneous DNA damage syndromes, which are caused by mutations in proteins of the DNA repair, share laboratory and clinical features also seen in autoimmune disorders and interferonopathies; hence a potential role of DNA-damage-induced type I IFN secretion seems likely. Here, we aim to summarize possible mechanisms of IFN induction in cutaneous DNA damage syndromes with defects in the DNA double-strand repair and nucleotide excision repair. We review recent publications referring to Ataxia teleangiectasia, Bloom syndrome, Rothmund-Thomson syndrome, Werner syndrome, Huriez syndrome, and Xeroderma pigmentosum. Furthermore, we aim to discuss the role of type I IFN in cancer and these syndromes.
Topics: Animals; Autoimmune Diseases; Biomarkers; Cellular Senescence; DNA Breaks, Double-Stranded; DNA Damage; DNA Repair; Diagnosis, Differential; Disease Management; Disease Susceptibility; Humans; Interferon Type I; Neoplasms; Skin; Syndrome
PubMed: 34381458
DOI: 10.3389/fimmu.2021.715723 -
Methods in Molecular Biology (Clifton,... 2018The highly complex structural genome variations chromothripsis, chromoanasynthesis, and chromoplexy are subsumed under the term chromoanagenesis, which means chromosome... (Review)
Review
The highly complex structural genome variations chromothripsis, chromoanasynthesis, and chromoplexy are subsumed under the term chromoanagenesis, which means chromosome rebirth. Precipitated by numerous DNA double-strand breaks, they differ in number of and distances between breakpoints, associated copy number variations, order and orientation of segments, and flanking sequences at joining points. Results from patients with the autosomal dominant cancer susceptibility disorder Li-Fraumeni syndrome implicated somatic TP53 mutations in chromothripsis. TP53 participates in the G2/M phase checkpoint, halting cell cycling after premature chromosome compaction during the second half of the S phase, thus preventing chromosome shattering. By experimental TP53 ablation and micronucleus induction, one or a few isolated chromosomes underwent desynchronized replication and chromothripsis. Secondly, chromothripsis occurred after experimental induction of telomere crisis after which dicentric chromosomes sustained TREX1-mediated resolution of chromosome bridges and kataegis. Third, DNA polymerase Polθ-dependent chromothripsis has been documented. Finally, a family with chromothripsis after L1 element-dependent retrotransposition and Alu/Alu homologous recombination has been reported. Human chromosomal instability syndromes share defects in responses to DNA double-strand breaks, characteristic cell cycle perturbations, elevated rates of micronucleus formation, premature chromosome compaction, and apoptosis. They are also associated with elevated susceptibility to malignant disease, such as medulloblastomas and gliomas in ataxia-telangiectasia, leukemia and lymphoma in Bloom syndrome, and osteosarcoma and soft tissue sarcoma in Werner syndrome. The latter syndrome is characterized by a premature aging-like progressive decline of mesenchymal tissues. In all thus far studied cases, constitutional chromothripsis occurred in the male germline and male patients with defects in the double-strand break response genes ATM, MRE11, BLM, LIG4, WRN, and Ku70 show impaired fertility. Conceivably, chromothripsis may, in a stochastic rather than deterministic way, be implicated in germline structural variation, malignant disease, premature aging, genome mosaicism in somatic tissues, and male infertility.
Topics: Animals; Cell Cycle; Chromothripsis; DNA Breaks, Double-Stranded; DNA Repair; DNA-Binding Proteins; Genes; Germ Cells; Humans; Mice; Micronuclei, Chromosome-Defective; Mutation; Retroelements; Signal Transduction; Telomere; Tumor Suppressor Protein p53
PubMed: 29564828
DOI: 10.1007/978-1-4939-7780-2_15 -
The Journal of Physical Chemistry. B Jun 2023The link between the chemical stability of G-quadruplex (qDNA) structures and their roles in eukaryotic genomic maintenance processes has been an area of interest now... (Review)
Review
The link between the chemical stability of G-quadruplex (qDNA) structures and their roles in eukaryotic genomic maintenance processes has been an area of interest now for several decades. This Review seeks to demonstrate how single-molecule force-based techniques can provide insight into the mechanical stabilities of a variety of qDNA structures as well as their ability to interconvert between different conformations under conditions of stress. Atomic force microscopy (AFM) and magnetic and optical tweezers have been the primary tools used in these investigations and have been used to examine both free and ligand-stabilized G-quadruplex structures. These studies have shown that the degree of stabilization of G-quadruplex structures has a significant effect on the ability of nuclear machinery to bypass these roadblocks on DNA strands. This Review will illustrate how various cellular components including replication protein A (RPA), Bloom syndrome protein (BLM), and Pif1 helicases are capable of unfolding qDNA. Techniques such as single-molecule fluorescence resonance energy transfer (smFRET), often in conjunction with the aforementioned force-based techniques, have proven extremely effective at elucidating the factors underpinning the mechanisms by which these proteins unwind qDNA structures. We will provide insight into how single-molecule tools have facilitated the direct visualization of qDNA roadblocks and also showcase results obtained from experiments designed to examine the ability of G-quadruplexes to limit the access of specific cellular proteins normally associated with telomeres.
Topics: G-Quadruplexes; DNA; Nanotechnology; Microscopy, Atomic Force; Telomere; Biology
PubMed: 37312244
DOI: 10.1021/acs.jpcb.3c01708 -
Scientific Reports Jan 2021Bloom Syndrome (BS; OMIM #210900; ORPHA #125) is a rare genetic disorder that is associated with growth deficits, compromised immune system, insulin resistance, genome...
Bloom Syndrome (BS; OMIM #210900; ORPHA #125) is a rare genetic disorder that is associated with growth deficits, compromised immune system, insulin resistance, genome instability and extraordinary predisposition to cancer. Most efforts thus far have focused on understanding the role of the Bloom syndrome DNA helicase BLM as a recombination factor in maintaining genome stability and suppressing cancer. Here, we observed increased levels of reactive oxygen species (ROS) and DNA base damage in BLM-deficient cells, as well as oxidative-stress-dependent reduction in DNA replication speed. BLM-deficient cells exhibited increased mitochondrial mass, upregulation of mitochondrial transcription factor A (TFAM), higher ATP levels and increased respiratory reserve capacity. Cyclin B1, which acts in complex with cyclin-dependent kinase CDK1 to regulate mitotic entry and associated mitochondrial fission by phosphorylating mitochondrial fission protein Drp1, fails to be fully degraded in BLM-deficient cells and shows unscheduled expression in G1 phase cells. This failure to degrade cyclin B1 is accompanied by increased levels and persistent activation of Drp1 throughout mitosis and into G1 phase as well as mitochondrial fragmentation. This study identifies mitochondria-associated abnormalities in Bloom syndrome patient-derived and BLM-knockout cells and we discuss how these abnormalities may contribute to Bloom syndrome.
Topics: Autophagy; Bloom Syndrome; Cyclin B1; DNA Damage; DNA Replication; DNA-Binding Proteins; Energy Metabolism; Fibroblasts; G1 Phase; Humans; Mitochondria; Mitochondrial Proteins; Mitosis; Oxidative Stress; Reactive Oxygen Species; RecQ Helicases; Transcription Factors; Up-Regulation
PubMed: 33495511
DOI: 10.1038/s41598-021-81075-0 -
Archives of Microbiology Apr 2023Cyanometabolites are active compounds derived from cyanobacteria that include small low molecular weight peptides, oligosaccharides, lectins, phenols, fatty acids, and... (Review)
Review
Cyanometabolites are active compounds derived from cyanobacteria that include small low molecular weight peptides, oligosaccharides, lectins, phenols, fatty acids, and alkaloids. Some of these compounds may pose a threat to human and environment. However, majority of them are known to have various health benefits with antiviral properties against pathogenic viruses including Human immunodeficiency virus (HIV), Ebola virus (EBOV), Herpes simplex virus (HSV), Influenza A virus (IAV) etc. Cyanometabolites classified as lectins include scytovirin (SVN), Oscillatoria agardhii agglutinin (OAAH), cyanovirin-N (CV-N), Microcystis viridis lectin (MVL), and microvirin (MVN) also possess a potent antiviral activity against viral diseases with unique properties to recognize different viral epitopes. Studies showed that a small linear peptide, microginin FR1, isolated from a water bloom of Microcystis species, inhibits angiotensin-converting enzyme (ACE), making it useful for the treatment of coronavirus disease 2019 (COVID-19). Our review provides an overview of the antiviral properties of cyanobacteria from the late 90s till now and emphasizes the significance of their metabolites in combating viral diseases, particularly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has received limited attention in previous publications. The enormous medicinal potential of cyanobacteria is also emphasized in this review, which justifies their use as a dietary supplement to fend off pandemics in future.
Topics: Humans; Antiviral Agents; COVID-19; SARS-CoV-2; Lectins; Cyanobacteria
PubMed: 37012452
DOI: 10.1007/s00203-023-03514-y -
BioRxiv : the Preprint Server For... Jan 2023Bloom syndrome helicase (BLM) is a RecQ-family helicase implicated in a variety of cellular processes, including DNA replication, DNA repair, and telomere maintenance....
Bloom syndrome helicase (BLM) is a RecQ-family helicase implicated in a variety of cellular processes, including DNA replication, DNA repair, and telomere maintenance. Mutations in human cause Bloom syndrome (BS), an autosomal recessive disorder that leads to myriad negative health impacts including a predisposition to cancer. BS-causing mutations in often negatively impact BLM ATPase and helicase activity. While mutations that cause BS have been well characterized both and , there are other less studied mutations that exist in the human population that do not lead to BS. Two of these non-BS mutations, encoding BLM P868L and BLM G1120R, when homozygous, increase sister chromatid exchanges in human cells. To characterize these naturally occurring BLM mutant proteins , we purified the BLM catalytic core (BLM , residues 636-1298) with either the P868L or G1120R substitution. We also purified a BLM K869A K870A mutant protein, which alters a lysine-rich loop proximal to the P868 residue. We found that BLM P868L and G1120R proteins were both able to hydrolyze ATP, bind diverse DNA substrates, and unwind G-quadruplex and duplex DNA structures. Molecular dynamics simulations suggest that the P868L substitution weakens the DNA interaction with the winged-helix domain of BLM and alters the orientation of one lobe of the ATPase domain. Because BLM P868L and G1120R retain helicase function , it is likely that the increased genome instability is caused by specific impacts of the mutant proteins . Interestingly, we found that BLM K869A K870A has diminished ATPase activity, weakened binding to duplex DNA structures, and less robust helicase activity compared to wild-type BLM . Thus, the lysine-rich loop may have an important role in ATPase activity and specific binding and DNA unwinding functions in BLM.
PubMed: 36747637
DOI: 10.1101/2023.01.26.525669 -
Proceedings of the National Academy of... Feb 2022The RecQ-like helicase BLM cooperates with topoisomerase IIIα, RMI1, and RMI2 in a heterotetrameric complex (the "Bloom syndrome complex") for dissolution of double...
The RecQ-like helicase BLM cooperates with topoisomerase IIIα, RMI1, and RMI2 in a heterotetrameric complex (the "Bloom syndrome complex") for dissolution of double Holliday junctions, key intermediates in homologous recombination. Mutations in any component of the Bloom syndrome complex can cause genome instability and a highly cancer-prone disorder called Bloom syndrome. Some heterozygous carriers are also predisposed to breast cancer. To understand how the activities of BLM helicase and topoisomerase IIIα are coupled, we purified the active four-subunit complex. Chemical cross-linking and mass spectrometry revealed a unique architecture that links the helicase and topoisomerase domains. Using biochemical experiments, we demonstrated dimerization mediated by the N terminus of BLM with a 2:2:2:2 stoichiometry within the Bloom syndrome complex. We identified mutations that independently abrogate dimerization or association of BLM with RMI1, and we show that both are dysfunctional for dissolution using in vitro assays and cause genome instability and synthetic lethal interactions with GEN1/MUS81 in cells. Truncated BLM can also inhibit the activity of full-length BLM in mixed dimers, suggesting a putative mechanism of dominant-negative action in carriers of BLM truncation alleles. Our results identify critical molecular determinants of Bloom syndrome complex assembly required for double Holliday junction dissolution and maintenance of genome stability.
Topics: Alleles; Bloom Syndrome; Carrier Proteins; Cell Line; DNA Topoisomerases, Type I; DNA, Cruciform; Genomic Instability; Humans; Mutation; Protein Binding; RecQ Helicases; Recombination, Genetic; Solubility
PubMed: 35115399
DOI: 10.1073/pnas.2109093119 -
Current Opinion in Nephrology and... Nov 2017With improving short-term kidney transplant outcomes, recurrent glomerular disease is being increasingly recognized as an important cause of chronic allograft failure.... (Review)
Review
PURPOSE OF REVIEW
With improving short-term kidney transplant outcomes, recurrent glomerular disease is being increasingly recognized as an important cause of chronic allograft failure. Further understanding of the risks and pathogenesis of recurrent glomerular disease enable informed transplant decisions, along with the development of preventive and treatment strategies.
RECENT FINDINGS
Multiple observational studies have highlighted differences in rates and outcomes for various recurrent glomerular diseases, although these rates have not markedly improved over the last decade. Emerging evidence supports use of rituximab to treat recurrent primary membranous nephropathy and possibly focal segmental glomerulosclerosis (FSGS), whereas eculizumab is effective in glomerular diseases associated with complement dysregulation [C3 glomerulopathy (C3G) and atypical hemolytic uremic syndrome (aHUS)].
SUMMARY
Despite the potential for recurrence in the allograft, transplant remains the optimal therapy for patients with advanced chronic kidney disease (CKD) secondary to primary glomerular disease. Biomarkers and therapeutic options necessitate accurate pretransplant diagnoses with opportunities for improved surveillance and treatment of recurrent glomerular disease posttransplant.
Topics: Antibodies, Monoclonal, Humanized; Atypical Hemolytic Uremic Syndrome; Chronic Disease; Glomerulonephritis; Humans; Immunologic Factors; Kidney Transplantation; Recurrence; Renal Insufficiency, Chronic; Rituximab
PubMed: 28832357
DOI: 10.1097/MNH.0000000000000358