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Movement of the RecG Motor Domain upon DNA Binding Is Required for Efficient Fork Reversal.
Warren GM, Stein RA, Mchaourab HS, Eichman BF
(2018) Int J Mol Sci 19:
MeSH Terms: DNA, DNA Helicases, DNA Replication, DNA-Binding Proteins, Models, Molecular, Molecular Conformation, Mutation, Nucleic Acid Conformation, Protein Binding, Protein Interaction Domains and Motifs, Structure-Activity Relationship
Show Abstract · Added August 26, 2019
RecG catalyzes reversal of stalled replication forks in response to replication stress in bacteria. The protein contains a fork recognition ("wedge") domain that binds branched DNA and a superfamily II (SF2) ATPase motor that drives translocation on double-stranded (ds)DNA. The mechanism by which the wedge and motor domains collaborate to catalyze fork reversal in RecG and analogous eukaryotic fork remodelers is unknown. Here, we used electron paramagnetic resonance (EPR) spectroscopy to probe conformational changes between the wedge and ATPase domains in response to fork DNA binding by RecG. Upon binding DNA, the ATPase-C lobe moves away from both the wedge and ATPase-N domains. This conformational change is consistent with a model of RecG fully engaged with a DNA fork substrate constructed from a crystal structure of RecG bound to a DNA junction together with recent cryo-electron microscopy (EM) structures of chromatin remodelers in complex with dsDNA. We show by mutational analysis that a conserved loop within the translocation in RecG (TRG) motif that was unstructured in the RecG crystal structure is essential for fork reversal and DNA-dependent conformational changes. Together, this work helps provide a more coherent model of fork binding and remodeling by RecG and related eukaryotic enzymes.
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The HIRAN domain of helicase-like transcription factor positions the DNA translocase motor to drive efficient DNA fork regression.
Chavez DA, Greer BH, Eichman BF
(2018) J Biol Chem 293: 8484-8494
MeSH Terms: DNA Helicases, DNA Replication, DNA, Single-Stranded, DNA-Binding Proteins, Humans, Protein Domains, Transcription Factors
Show Abstract · Added August 26, 2019
Helicase-like transcription factor (HLTF) is a central mediator of the DNA damage response and maintains genome stability by regressing stalled replication forks. The N-terminal HIRAN domain binds specifically to the 3'-end of single-stranded DNA (ssDNA), and disrupting this function interferes with fork regression as well as replication fork progression in cells under replication stress. Here, we investigated the mechanism by which the HIRAN-ssDNA interaction facilitates fork remodeling. Our results indicated that HIRAN capture of a denatured nascent leading 3'-end directs specific binding of HLTF to forks. DNase footprinting revealed that HLTF binds to the parental duplex ahead of the fork and at the leading edge behind the fork. Moreover, we found that the HIRAN domain is important for initiating regression of forks when both nascent strands are at the junction, but is dispensable when forks contain ssDNA regions on either template strand. We also found that HLTF catalyzes fork restoration from a partially regressed structure in a HIRAN-dependent manner. Thus, HIRAN serves as a substrate-recognition domain to properly orient the ATPase motor domain at stalled and regressed forks and initiates fork remodeling by guiding formation of a four-way junction. We discuss how these activities compare with those of two related fork remodelers, SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A-like 1 (SMARCAL1) and zinc finger RANBP2 type-containing 3 (ZRANB3) to provide insight into their nonredundant roles in DNA damage tolerance.
© 2018 Chavez et al.
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Autochthonous tumors driven by loss have an ongoing requirement for the RBP2 histone demethylase.
McBrayer SK, Olenchock BA, DiNatale GJ, Shi DD, Khanal J, Jennings RB, Novak JS, Oser MG, Robbins AK, Modiste R, Bonal D, Moslehi J, Bronson RT, Neuberg D, Nguyen QD, Signoretti S, Losman JA, Kaelin WG
(2018) Proc Natl Acad Sci U S A 115: E3741-E3748
MeSH Terms: Alleles, Animals, DNA-Binding Proteins, Echocardiography, Enzyme Activation, Fibroblasts, Genes, Retinoblastoma, Heart Septal Defects, Histone Code, Integrases, Jumonji Domain-Containing Histone Demethylases, Mice, Mice, Inbred C57BL, Molecular Targeted Therapy, Neoplasm Proteins, Pituitary Neoplasms, Recombinant Fusion Proteins, Retinoblastoma Protein, Tamoxifen, Thyroid Neoplasms, Transgenes
Show Abstract · Added April 22, 2018
Inactivation of the retinoblastoma gene () product, pRB, is common in many human cancers. Targeting downstream effectors of pRB that are central to tumorigenesis is a promising strategy to block the growth of tumors harboring loss-of-function mutations. One such effector is retinoblastoma-binding protein 2 (RBP2, also called JARID1A or KDM5A), which encodes an H3K4 demethylase. Binding of pRB to RBP2 has been linked to the ability of pRB to promote senescence and differentiation. Importantly, genetic ablation of RBP2 is sufficient to phenocopy pRB's ability to induce these cellular changes in cell culture experiments. Moreover, germline deletion significantly impedes tumorigenesis in mice. The value of RBP2 as a therapeutic target in cancer, however, hinges on whether loss of RBP2 could block the growth of established tumors as opposed to simply delaying their onset. Here we show that conditional, systemic ablation of RBP2 in tumor-bearing mice is sufficient to slow tumor growth and significantly extend survival without causing obvious toxicity to the host. These findings show that established -null tumors require RBP2 for growth and further credential RBP2 as a therapeutic target in human cancers driven by inactivation.
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ARID1A Maintains Differentiation of Pancreatic Ductal Cells and Inhibits Development of Pancreatic Ductal Adenocarcinoma in Mice.
Kimura Y, Fukuda A, Ogawa S, Maruno T, Takada Y, Tsuda M, Hiramatsu Y, Araki O, Nagao M, Yoshikawa T, Ikuta K, Yoshioka T, Wang Z, Akiyama H, Wright CV, Takaori K, Uemoto S, Chiba T, Seno H
(2018) Gastroenterology 155: 194-209.e2
MeSH Terms: Adenocarcinoma in Situ, Animals, Carcinogenesis, Carcinoma, Pancreatic Ductal, Cell Culture Techniques, Cell Differentiation, DNA-Binding Proteins, Mice, Nuclear Proteins, Pancreatic Ducts, Pancreatic Neoplasms, Proto-Oncogene Proteins p21(ras), SOX9 Transcription Factor
Show Abstract · Added April 3, 2018
BACKGROUND & AIMS - The ARID1A gene encodes a protein that is part of the large adenosine triphosphate (ATP)-dependent chromatin remodeling complex SWI/SNF and is frequently mutated in human pancreatic ductal adenocarcinomas (PDACs). We investigated the functions of ARID1A during formation of PDACs in mice.
METHODS - We performed studies with Ptf1a-Cre;Kras mice, which express activated Kras in the pancreas and develop pancreatic intraepithelial neoplasias (PanINs), as well as those with disruption of Aird1a (Ptf1a-Cre;Kras;Arid1a mice) or disruption of Brg1 (encodes a catalytic ATPase of the SWI/SNF complex) (Ptf1a-Cre;Kras; Brg1mice). Pancreatic ductal cells (PDCs) were isolated from Arid1a mice and from Arid1a;SOX9OE mice, which overexpress human SOX9 upon infection with an adenovirus-expressing Cre recombinase. Pancreatic tissues were collected from all mice and analyzed by histology and immunohistochemistry; cells were isolated and grown in 2-dimensional and 3-dimensional cultures. We performed microarray analyses to compare gene expression patterns in intraductal papillary mucinous neoplasms (IPMNs) from the different strains of mice. We obtained 58 samples of IPMNs and 44 samples of PDACs from patients who underwent pancreatectomy in Japan and analyzed them by immunohistochemistry.
RESULTS - Ptf1a-Cre;Kras mice developed PanINs, whereas Ptf1a-Cre;Kras;Arid1a mice developed IPMNs and PDACs; IPMNs originated from PDCs. ARID1A-deficient IPMNs did not express SOX9. ARID1A-deficient PDCs had reduced expression of SOX9 and dedifferentiated in culture. Overexpression of SOX9 in these cells allowed them to differentiate and prevented dilation of ducts. Among mice with pancreatic expression of activated Kras, those with disruption of Arid1a developed fewer PDACs from IPMNs than mice with disruption of Brg1. ARID1A-deficient IPMNs had reduced activity of the mTOR pathway. Human IPMN and PDAC specimens had reduced levels of ARID1A, SOX9, and phosphorylated S6 (a marker of mTOR pathway activation). Levels of ARID1A correlated with levels of SOX9 and phosphorylated S6.
CONCLUSIONS - ARID1A regulates expression of SOX9, activation of the mTOR pathway, and differentiation of PDCs. ARID1A inhibits formation of PDACs from IPMNs in mice with pancreatic expression of activated KRAS and is down-regulated in IPMN and PDAC tissues from patients.
Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.
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The receptor tyrosine kinase EphA2 promotes glutamine metabolism in tumors by activating the transcriptional coactivators YAP and TAZ.
Edwards DN, Ngwa VM, Wang S, Shiuan E, Brantley-Sieders DM, Kim LC, Reynolds AB, Chen J
(2017) Sci Signal 10:
MeSH Terms: Adaptor Proteins, Signal Transducing, Amino Acid Transport System ASC, Animals, Biomarkers, Tumor, Breast Neoplasms, DNA-Binding Proteins, Disease Models, Animal, Ephrin-A2, Female, Glutaminase, Glutamine, Humans, Intracellular Signaling Peptides and Proteins, Mice, Mice, Knockout, Minor Histocompatibility Antigens, Muscle Proteins, Phosphoproteins, Transcription Factors, Tumor Cells, Cultured
Show Abstract · Added April 2, 2019
Malignant tumors reprogram cellular metabolism to support cancer cell proliferation and survival. Although most cancers depend on a high rate of aerobic glycolysis, many cancer cells also display addiction to glutamine. Glutamine transporters and glutaminase activity are critical for glutamine metabolism in tumor cells. We found that the receptor tyrosine kinase EphA2 activated the TEAD family transcriptional coactivators YAP and TAZ (YAP/TAZ), likely in a ligand-independent manner, to promote glutamine metabolism in cells and mouse models of HER2-positive breast cancer. Overexpression of EphA2 induced the nuclear accumulation of YAP and TAZ and increased the expression of YAP/TAZ target genes. Inhibition of the GTPase Rho or the kinase ROCK abolished EphA2-dependent YAP/TAZ nuclear localization. Silencing or substantially reduced the amount of intracellular glutamate through decreased expression of and , respectively, genes that encode proteins that promote glutamine uptake and metabolism. The regulatory DNA elements of both and contain TEAD binding sites and were bound by TEAD4 in an EphA2-dependent manner. In patient breast cancer tissues, expression positively correlated with that of and , as well as that of and Although high expression of predicted enhanced metastatic potential and poor patient survival, it also rendered HER2-positive breast cancer cells more sensitive to glutaminase inhibition. The findings define a previously unknown mechanism of EphA2-mediated glutaminolysis through YAP/TAZ activation in HER2-positive breast cancer and identify potential therapeutic targets in patients.
Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
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Separate transcriptionally regulated pathways specify distinct classes of sister dendrites in a nociceptive neuron.
O'Brien BMJ, Palumbos SD, Novakovic M, Shang X, Sundararajan L, Miller DM
(2017) Dev Biol 432: 248-257
MeSH Terms: Animals, Caenorhabditis elegans, Caenorhabditis elegans Proteins, DNA-Binding Proteins, Dendrites, Gene Expression Regulation, LIM-Homeodomain Proteins, Membrane Proteins, Nociceptors, Regulatory Elements, Transcriptional, Sensory Receptor Cells, Transcription Factors, Zinc Fingers
Show Abstract · Added March 26, 2019
The dendritic processes of nociceptive neurons transduce external signals into neurochemical cues that alert the organism to potentially damaging stimuli. The receptive field for each sensory neuron is defined by its dendritic arbor, but the mechanisms that shape dendritic architecture are incompletely understood. Using the model nociceptor, the PVD neuron in C. elegans, we determined that two types of PVD lateral branches project along the dorsal/ventral axis to generate the PVD dendritic arbor: (1) Pioneer dendrites that adhere to the epidermis, and (2) Commissural dendrites that fasciculate with circumferential motor neuron processes. Previous reports have shown that the LIM homeodomain transcription factor MEC-3 is required for all higher order PVD branching and that one of its targets, the claudin-like membrane protein HPO-30, preferentially promotes outgrowth of pioneer branches. Here, we show that another MEC-3 target, the conserved TFIIA-like zinc finger transcription factor EGL-46, adopts the alternative role of specifying commissural dendrites. The known EGL-46 binding partner, the TEAD transcription factor EGL-44, is also required for PVD commissural branch outgrowth. Double mutants of hpo-30 and egl-44 show strong enhancement of the lateral branching defect with decreased numbers of both pioneer and commissural dendrites. Thus, HPO-30/Claudin and EGL-46/EGL-44 function downstream of MEC-3 and in parallel acting pathways to direct outgrowth of two distinct classes of PVD dendritic branches.
Copyright © 2017 Elsevier Inc. All rights reserved.
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Improved base excision repair inhibition and bacteriophage Mu Gam protein yields C:G-to-T:A base editors with higher efficiency and product purity.
Komor AC, Zhao KT, Packer MS, Gaudelli NM, Waterbury AL, Koblan LW, Kim YB, Badran AH, Liu DR
(2017) Sci Adv 3: eaao4774
MeSH Terms: Bacteriophage mu, Base Pairing, Cell Line, DNA Repair, DNA-Binding Proteins, Enzyme Activation, Gene Frequency, Gene Order, Humans, INDEL Mutation, Uracil-DNA Glycosidase, Viral Proteins
Show Abstract · Added March 21, 2018
We recently developed base editing, the programmable conversion of target C:G base pairs to T:A without inducing double-stranded DNA breaks (DSBs) or requiring homology-directed repair using engineered fusions of Cas9 variants and cytidine deaminases. Over the past year, the third-generation base editor (BE3) and related technologies have been successfully used by many researchers in a wide range of organisms. The product distribution of base editing-the frequency with which the target C:G is converted to mixtures of undesired by-products, along with the desired T:A product-varies in a target site-dependent manner. We characterize determinants of base editing outcomes in human cells and establish that the formation of undesired products is dependent on uracil N-glycosylase (UNG) and is more likely to occur at target sites containing only a single C within the base editing activity window. We engineered CDA1-BE3 and AID-BE3, which use cytidine deaminase homologs that increase base editing efficiency for some sequences. On the basis of these observations, we engineered fourth-generation base editors (BE4 and SaBE4) that increase the efficiency of C:G to T:A base editing by approximately 50%, while halving the frequency of undesired by-products compared to BE3. Fusing BE3, BE4, SaBE3, or SaBE4 to Gam, a bacteriophage Mu protein that binds DSBs greatly reduces indel formation during base editing, in most cases to below 1.5%, and further improves product purity. BE4, SaBE4, BE4-Gam, and SaBE4-Gam represent the state of the art in C:G-to-T:A base editing, and we recommend their use in future efforts.
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Camptothecin resistance is determined by the regulation of topoisomerase I degradation mediated by ubiquitin proteasome pathway.
Ando K, Shah AK, Sachdev V, Kleinstiver BP, Taylor-Parker J, Welch MM, Hu Y, Salgia R, White FM, Parvin JD, Ozonoff A, Rameh LE, Joung JK, Bharti AK
(2017) Oncotarget 8: 43733-43751
MeSH Terms: BRCA1 Protein, Camptothecin, Cell Line, Tumor, DNA Topoisomerases, Type I, DNA-Binding Proteins, Drug Resistance, Neoplasm, Gene Editing, Humans, Ku Autoantigen, Multiprotein Complexes, PTEN Phosphohydrolase, Phosphorylation, Proteasome Endopeptidase Complex, Protein Binding, Protein Kinase C, Proteolysis, RNA Interference, Topoisomerase I Inhibitors, Ubiquitin
Show Abstract · Added November 26, 2018
Proteasomal degradation of topoisomerase I (topoI) is one of the most remarkable cellular phenomena observed in response to camptothecin (CPT). Importantly, the rate of topoI degradation is linked to CPT resistance. Formation of the topoI-DNA-CPT cleavable complex inhibits DNA re-ligation resulting in DNA-double strand break (DSB). The degradation of topoI marks the first step in the ubiquitin proteasome pathway (UPP) dependent DNA damage response (DDR). Here, we show that the Ku70/Ku80 heterodimer binds with topoI, and that the DNA-dependent protein kinase (DNA-PKcs) phosphorylates topoI on serine 10 (topoI-pS10), which is subsequently ubiquitinated by BRCA1. A higher basal level of topoI-pS10 ensures rapid topoI degradation leading to CPT resistance. Importantly, PTEN regulates DNA-PKcs kinase activity in this pathway and PTEN deletion ensures DNA-PKcs dependent higher topoI-pS10, rapid topoI degradation and CPT resistance.
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Interleukin-22 drives nitric oxide-dependent DNA damage and dysplasia in a murine model of colitis-associated cancer.
Wang C, Gong G, Sheh A, Muthupalani S, Bryant EM, Puglisi DA, Holcombe H, Conaway EA, Parry NAP, Bakthavatchalu V, Short SP, Williams CS, Wogan GN, Tannenbaum SR, Fox JG, Horwitz BH
(2017) Mucosal Immunol 10: 1504-1517
MeSH Terms: Animals, Antibodies, Blocking, Colitis, Ulcerative, Colon, Colonic Neoplasms, DNA Breaks, Double-Stranded, DNA-Binding Proteins, Disease Models, Animal, Helicobacter Infections, Helicobacter hepaticus, Humans, Inflammation, Interleukins, Macrophages, Peritoneal, Mice, Mice, 129 Strain, Mice, Knockout, Neoplasms, Nitric Oxide, Nitric Oxide Synthase Type II
Show Abstract · Added April 15, 2019
The risk of colon cancer is increased in patients with Crohn's disease and ulcerative colitis. Inflammation-induced DNA damage could be an important link between inflammation and cancer, although the pathways that link inflammation and DNA damage are incompletely defined. RAG2-deficient mice infected with Helicobacter hepaticus (Hh) develop colitis that progresses to lower bowel cancer. This process depends on nitric oxide (NO), a molecule with known mutagenic potential. We have previously hypothesized that production of NO by macrophages could be essential for Hh-driven carcinogenesis, however, whether Hh infection induces DNA damage in this model and whether this depends on NO has not been determined. Here we demonstrate that Hh infection of RAG2-deficient mice rapidly induces expression of iNOS and the development of DNA double-stranded breaks (DSBs) specifically in proliferating crypt epithelial cells. Generation of DSBs depended on iNOS activity, and further, induction of iNOS, the generation of DSBs, and the subsequent development of dysplasia were inhibited by depletion of the Hh-induced cytokine IL-22. These results demonstrate a strong association between Hh-induced DNA damage and the development of dysplasia, and further suggest that IL-22-dependent induction of iNOS within crypt epithelial cells rather than macrophages is a driving force in this process.
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The LIM protein complex establishes a retinal circuitry of visual adaptation by regulating Pax6 α-enhancer activity.
Kim Y, Lim S, Ha T, Song YH, Sohn YI, Park DJ, Paik SS, Kim-Kaneyama JR, Song MR, Leung A, Levine EM, Kim IB, Goo YS, Lee SH, Kang KH, Kim JW
(2017) Elife 6:
MeSH Terms: Adaptation, Ocular, Animals, Cytoskeletal Proteins, DNA-Binding Proteins, Enhancer Elements, Genetic, Gene Expression Regulation, LIM Domain Proteins, LIM-Homeodomain Proteins, Mice, Mice, Knockout, PAX6 Transcription Factor, Retina, Transcription Factors
Show Abstract · Added February 14, 2018
The visual responses of vertebrates are sensitive to the overall composition of retinal interneurons including amacrine cells, which tune the activity of the retinal circuitry. The expression of is regulated by multiple cis-DNA elements including the intronic α-enhancer, which is active in GABAergic amacrine cell subsets. Here, we report that the transforming growth factor ß1-induced transcript 1 protein (Tgfb1i1) interacts with the LIM domain transcription factors Lhx3 and Isl1 to inhibit the α-enhancer in the post-natal mouse retina. mice show elevated α-enhancer activity leading to overproduction of Pax6ΔPD isoform that supports the GABAergic amacrine cell fate maintenance. Consequently, the mouse retinas show a sustained light response, which becomes more transient in mice with the auto-stimulation-defective mutation. Together, we show the antagonistic regulation of the α-enhancer activity by Pax6 and the LIM protein complex is necessary for the establishment of an inner retinal circuitry, which controls visual adaptation.
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