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Current Biology : CB Jan 2017In most sexually reproducing organisms, crossover formation between homologous chromosomes is necessary for proper chromosome disjunction during meiosis I. During...
In most sexually reproducing organisms, crossover formation between homologous chromosomes is necessary for proper chromosome disjunction during meiosis I. During meiotic recombination, a subset of programmed DNA double-strand breaks (DSBs) are repaired as crossovers, with the remainder becoming noncrossovers [1]. Whether a repair intermediate is designated to become a crossover is a highly regulated decision that integrates several crossover patterning processes, both along chromosome arms (interference and the centromere effect) and between chromosomes (crossover assurance) [2]. Because the mechanisms that generate crossover patterning have remained elusive for over a century, it has been difficult to assess the relationship between crossover patterning and meiotic chromosome behavior. We show here that meiotic crossover patterning is lost in Drosophila melanogaster mutants that lack the Bloom syndrome helicase. In the absence of interference and the centromere effect, crossovers are distributed more uniformly along chromosomes. Crossovers even occur on the small chromosome 4, which normally never has meiotic crossovers [3]. Regulated distribution of crossovers between chromosome pairs is also lost, resulting in an elevated frequency of homologs that do not receive a crossover, which in turn leads to elevated nondisjunction.
Topics: Animals; DNA Helicases; Drosophila Proteins; Drosophila melanogaster; Female; Homologous Recombination; Male; Meiosis; Nondisjunction, Genetic
PubMed: 27989672
DOI: 10.1016/j.cub.2016.10.055 -
Trends in Biochemical Sciences Sep 2014Holliday junctions (HJs) are four-stranded DNA intermediates that arise during the recombinational repair of DNA double-strand breaks (DSBs). Their timely removal is... (Review)
Review
Holliday junctions (HJs) are four-stranded DNA intermediates that arise during the recombinational repair of DNA double-strand breaks (DSBs). Their timely removal is crucial for faithful chromosome segregation and genome stability. In mammalian cells, HJs are processed by the BTR (BLM-topoisomerase IIIα-RMI1-RMI2) complex, the SLX-MUS (SLX1-SLX4-MUS81-EME1) complex, and the GEN1 resolvase. Recent studies have linked the deficiency of one or more of these enzymes to perturbed DNA replication, impaired crosslink repair, chromosomal instability, and defective mitoses, coupled with the transmission of widespread DNA damage and high levels of mortality. We review these key advances and how they have cemented the status of HJ-processing enzymes as guardians of genome integrity and viability in mammalian cells.
Topics: Animals; DNA Damage; DNA Replication; DNA, Cruciform; Genomic Instability; Holliday Junction Resolvases; Humans; Recombination, Genetic
PubMed: 25131815
DOI: 10.1016/j.tibs.2014.07.003 -
Frontiers in Genetics 2014The RecQ family DNA helicases Werner syndrome protein (WRN) and Bloom syndrome protein (BLM) play a key role in protecting the genome against deleterious changes. In... (Review)
Review
The RecQ family DNA helicases Werner syndrome protein (WRN) and Bloom syndrome protein (BLM) play a key role in protecting the genome against deleterious changes. In humans, mutations in these proteins lead to rare genetic diseases associated with cancer predisposition and accelerated aging. WRN and BLM are distinguished from other helicases by possessing signature tandem domains toward the C terminus, referred to as the RecQ C-terminal (RQC) and helicase-and-ribonuclease D-C-terminal (HRDC) domains. Although the precise function of the HRDC domain remains unclear, the previous crystal structure of a WRN RQC-DNA complex visualized a central role for the RQC domain in recognizing, binding and unwinding DNA at branch points. In particular, a prominent hairpin structure (the β-wing) within the RQC winged-helix motif acts as a scalpel to induce the unpairing of a Watson-Crick base pair at the DNA duplex terminus. A similar RQC-DNA interaction was also observed in the recent crystal structure of a BLM-DNA complex. I review the latest structures of WRN and BLM, and then provide a docking simulation of BLM with a Holliday junction. The model offers an explanation for the efficient branch migration activity of the RecQ family toward recombination and repair intermediates.
PubMed: 25400656
DOI: 10.3389/fgene.2014.00366 -
Oxidative Medicine and Cellular... 2019Prostate cancer (PC) is a common malignant tumor and a leading cause of cancer-related death in men worldwide. In order to design new therapeutic interventions for PC,...
PURPOSE
Prostate cancer (PC) is a common malignant tumor and a leading cause of cancer-related death in men worldwide. In order to design new therapeutic interventions for PC, an understanding of the molecular events underlying PC tumorigenesis is required. Bloom syndrome protein (BLM) is a RecQ-like helicase, which helps maintain genetic stability. BLM dysfunction has been implicated in tumor development, most recently during PC tumorigenesis. However, the molecular basis for BLM-induced PC progression remains poorly characterized. In this study, we investigated whether BLM modulates the phosphorylation of an array of prooncogenic signaling pathways to promote PC progression.
METHODS
We analyzed differentially expressed proteins (DEPs) using iTRAQ technology. Site-directed knockout of BLM in PC-3 prostate cancer cells was performed using CRISPR/Cas9-mediated homologous recombination gene editing to confirm the effects of BLM on DEPs. PathScan® Antibody Array Kits were used to analyze the phosphorylation of nodal proteins in PC tissue. Immunohistochemistry and automated western blot (WES) analyses were used to validate these findings.
RESULTS
We found that silencing BLM in PC-3 cells significantly reduced their proliferative capacity. In addition, BLM downregulation significantly reduced levels of phosphorylated protein kinase B (AKT (Ser473)) and proline-rich AKT substrate of 40 kDa (PRAS40 (Thr246)), and this was accompanied by enhanced ROS (reactive oxygen species) levels. In addition, we found that AKT and PRAS40 inhibition reduced BLM, increased ROS levels, and induced PC cell apoptosis.
CONCLUSIONS
We demonstrated that BLM activates AKT and PRAS40 to promote PC cell proliferation and survival. We further propose that ROS act in concert with BLM to facilitate PC oncogenesis, potentially via further enhancing AKT signaling and downregulating PTEN expression. Importantly, inhibiting the BLM-AKT-PRAS40 axis induced PC cell apoptosis. Thus, we highlight new avenues for novel anti-PC treatments.
Topics: Adaptor Proteins, Signal Transducing; Cell Proliferation; Cell Survival; Gene Expression Regulation, Neoplastic; Humans; Male; PC-3 Cells; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; RecQ Helicases
PubMed: 31210839
DOI: 10.1155/2019/3685817 -
Journal of the American Academy of... Nov 2016Hereditary photodermatoses are a spectrum of rare photosensitive disorders that are often caused by genetic deficiency or malfunction of various components of the DNA... (Review)
Review
Hereditary photodermatoses are a spectrum of rare photosensitive disorders that are often caused by genetic deficiency or malfunction of various components of the DNA repair pathway. This results clinically in extreme photosensitivity, with many syndromes exhibiting an increased risk of cutaneous malignancies. This review will focus specifically on the syndromes with malignant potential, including xeroderma pigmentosum, Bloom syndrome, and Rothmund-Thomson syndrome. The typical phenotypic findings of each disorder will be examined and contrasted, including noncutaneous identifiers to aid in diagnosis. The management of these patients will also be discussed. At this time, the mainstay of therapy remains strict photoprotection; however, genetic therapies are under investigation.
Topics: Bloom Syndrome; DNA Repair; DNA Repair Enzymes; DNA Repair-Deficiency Disorders; Genes, Recessive; Genetic Predisposition to Disease; Humans; Neoplasms, Radiation-Induced; Neoplastic Syndromes, Hereditary; Phenotype; Photosensitivity Disorders; Proliferating Cell Nuclear Antigen; Rothmund-Thomson Syndrome; Skin Neoplasms; Sunlight; Ultraviolet Rays; Xeroderma Pigmentosum
PubMed: 27745641
DOI: 10.1016/j.jaad.2016.03.045 -
Pediatric Blood & Cancer Nov 2023
Topics: Humans; Bloom Syndrome; Hematologic Neoplasms; Hematopoietic Stem Cell Transplantation
PubMed: 37644665
DOI: 10.1002/pbc.30655 -
Journal of Pediatric Hematology/oncology Mar 2024Bloom syndrome (BS) is a rare autosomal recessive inherited disorder. Patients with BS have photosensitivity, telangiectatic facial erythema, and stunted growth. They...
Bloom syndrome (BS) is a rare autosomal recessive inherited disorder. Patients with BS have photosensitivity, telangiectatic facial erythema, and stunted growth. They usually have mild microcephaly, and distinctive facial features such as a narrow, slender face, micrognathism, and a prominent nose. Kostmann disease (KD) is a subgroup of severe congenital neutropenias. The diagnosis of severe congenital neutropenia is based on clinical symptoms, bone marrow findings, and genetic mutation. Here, we report a female patient with a triangular face, nasal prominence, and protruding ears presenting with recurrent infections and severe neutropenia. Molecular genetic testing revealed a compound heterozygous variant in the HCLS-1-associated protein X-1 gene [(c.130_131insA) p.(trp44*), c.430 dup(p.Val144fs)] and a new homozygous variant in Bloom Syndrome RecQ like helicase gene [c.2074+2T>C p.(?)]. She was diagnosed with both BS and KD. To the best of our knowledge, this is the first case of coexisting BS and KD in a patient ever reported.
Topics: Humans; Female; Bloom Syndrome; Congenital Bone Marrow Failure Syndromes; Neutropenia; Mutation
PubMed: 38113221
DOI: 10.1097/MPH.0000000000002798 -
Angewandte Chemie (International Ed. in... Sep 2022Bloom syndrome protein (BLM) is a conserved RecQ family helicase involved in the maintenance of genome stability. BLM has been widely recognized as a genome "caretaker"...
Bloom syndrome protein (BLM) is a conserved RecQ family helicase involved in the maintenance of genome stability. BLM has been widely recognized as a genome "caretaker" that processes structured DNA. In contrast, our knowledge of how BLM behaves on single-stranded (ss) DNA is still limited. Here, we demonstrate that BLM possesses the intrinsic ability for phase separation and can co-phase separate with ssDNA to form dynamically arrested protein/ssDNA co-condensates. The introduction of ATP potentiates the capability of BLM to condense on ssDNA, which further promotes the compression of ssDNA against a resistive force of up to 60 piconewtons. Moreover, BLM is also capable of condensing replication protein A (RPA)- or RAD51-coated ssDNA, before which it generates naked ssDNA by dismantling these ssDNA-binding proteins. Overall, our findings identify an unexpected characteristic of a DNA helicase and provide a new angle of protein/ssDNA co-condensation for understanding the genomic instability caused by BLM overexpression under diseased conditions.
Topics: Adenosine Triphosphate; Bloom Syndrome; DNA; DNA Repair; DNA, Single-Stranded; Genomic Instability; Humans; RecQ Helicases; Replication Protein A
PubMed: 35922882
DOI: 10.1002/anie.202209463 -
Frontiers in Pediatrics 2020DNA damage response is essential to human physiology. A broad spectrum of pathologies are displayed by individuals carrying monoallelic or biallelic loss-of-function... (Review)
Review
DNA damage response is essential to human physiology. A broad spectrum of pathologies are displayed by individuals carrying monoallelic or biallelic loss-of-function mutations in DNA damage repair genes. DNA repair syndromes with biallelic disturbance of essential DNA damage response pathways manifest early in life with multi-systemic involvement and a high propensity for hematologic and solid cancers, as well as bone marrow failure. In this review, we describe classic biallelic DNA repair cancer syndromes arising from faulty single- and double-strand DNA break repair, as well as dysfunctional DNA helicases. These clinical entities include xeroderma pigmentosum, constitutional mismatch repair deficiency, ataxia telangiectasia, Nijmegen breakage syndrome, deficiencies of DNA ligase IV, NHEJ/Cernunnos, and ERCC6L2, as well as Bloom, Werner, and Rothmund-Thompson syndromes. To give an in-depth understanding of these disorders, we provide historical overview and discuss the interplay between complex biology and heterogeneous clinical manifestations.
PubMed: 33194896
DOI: 10.3389/fped.2020.570084 -
Nature Communications May 2019The collapse of stalled replication forks is a major driver of genomic instability. Several committed mechanisms exist to resolve replication stress. These pathways are...
The collapse of stalled replication forks is a major driver of genomic instability. Several committed mechanisms exist to resolve replication stress. These pathways are particularly pertinent at telomeres. Cancer cells that use Alternative Lengthening of Telomeres (ALT) display heightened levels of telomere-specific replication stress, and co-opt stalled replication forks as substrates for break-induced telomere synthesis. FANCM is a DNA translocase that can form independent functional interactions with the BLM-TOP3A-RMI (BTR) complex and the Fanconi anemia (FA) core complex. Here, we demonstrate that FANCM depletion provokes ALT activity, evident by increased break-induced telomere synthesis, and the induction of ALT biomarkers. FANCM-mediated attenuation of ALT requires its inherent DNA translocase activity and interaction with the BTR complex, but does not require the FA core complex, indicative of FANCM functioning to restrain excessive ALT activity by ameliorating replication stress at telomeres. Synthetic inhibition of FANCM-BTR complex formation is selectively toxic to ALT cancer cells.
Topics: Carrier Proteins; Cell Line, Tumor; DNA Helicases; DNA Replication; DNA Topoisomerases, Type I; DNA-Binding Proteins; HCT116 Cells; HEK293 Cells; HeLa Cells; Humans; Neoplasms; Nuclear Proteins; RecQ Helicases; Telomere; Telomere Homeostasis
PubMed: 31138797
DOI: 10.1038/s41467-019-10180-6