Jacqueline J.l Jacobs - Academia.edu (original) (raw)
Papers by Jacqueline J.l Jacobs
Molecular & Cellular Proteomics
Loss of telomere protection: consequences and
Nature Communications
Protection of stalled replication forks is essential to prevent genome instability, a major drivi... more Protection of stalled replication forks is essential to prevent genome instability, a major driving force of tumorigenesis. Several key regulators of DNA double-stranded break (DSB) repair, including 53BP1 and RIF1, have been implicated in fork protection. MAD2L2, also known as REV7, plays an important role downstream of 53BP1/RIF1 by counteracting resection at DSBs in the recently discovered shieldin complex. The ability to bind and counteract resection at exposed DNA ends at DSBs makes MAD2L2/shieldin a prime candidate for also suppressing nucleolytic processing at stalled replication forks. However, the function of MAD2L2/shieldin outside of DNA repair is unknown. Here we address this by using genetic and single-molecule analyses and find that MAD2L2 is required for protecting and restarting stalled replication forks. MAD2L2 loss leads to uncontrolled MRE11-dependent resection of stalled forks and single-stranded DNA accumulation, which causes irreparable genomic damage. Unexpect...
Lazzerini Denchi for discussion. J.J. gratefully acknowledges discussion with Maarten van Lohuize... more Lazzerini Denchi for discussion. J.J. gratefully acknowledges discussion with Maarten van Lohuizen and Anton Berns. Work on the telomere damage response in the de Lange lab is supported by a grant from the NIH (AG16642). J.J. was supported by a Dutch Cancer Society Fellowship. Perspective p16INK4a as a Second Effector of the Telomere Damage Pathway Telomere damage resulting from telomere shortening can potentially suppress tumori-genesis by permanently arresting or eliminating incipient cancer cells. Dysfunctional telomeres activate the canonical DNA damage response pathway, resulting in a p53-mediated G1/S arrest and senescence or apoptosis. Experimental induction of telomere damage through inhibition of the telomeric protein TRF2 recapitulates aspects of telomere attrition, including a p53-mediated cell cycle arrest. Using this system, we have shown
This article cites 67 articles, 31 of which can be accessed free
Nucleus (Austin, Tex.), 2012
DNA repair activities at DNA double-strand breaks (DSBs) are under control of regulatory ubiquity... more DNA repair activities at DNA double-strand breaks (DSBs) are under control of regulatory ubiquitylation events governed by the RNF8 and RNF168 ubiquitin-ligases. Defects in this regulatory mechanism, as with mutation of other key DNA damage-response factors, lead to genomic instability and cancer, presumably due to impaired repair of DNA lesions. Recent work revealed that RNF8 and RNF168 also play critical roles at natural chromosome ends, when no longer adequately shielded by telomeres. In contrast to repair of DSBs being needed to maintain genome integrity, repair activities at telomeres create chromosome end-to-end fusions that threaten genome integrity. Upon cell division these telomere fusions give rise to genomic alterations and instability via chromosomal missegregration and initiation of breakage-fusion-bridge cycles. Here, I discuss the role of RNF8 at natural chromosome ends and its (potential) consequences.
Nature Cell Biology, 2011
Molecular and Cellular Biology, 2003
The polycomb protein Bmi-1 represses the INK4a locus, which encodes the tumor suppressors p16 and... more The polycomb protein Bmi-1 represses the INK4a locus, which encodes the tumor suppressors p16 and p14ARF. Here we report that Bmi-1 is downregulated when WI-38 human fibroblasts undergo replicative senescence, but not quiescence, and extends replicative life span when overexpressed. Life span extension by Bmi-1 required the pRb, but not p53, tumor suppressor protein. Deletion analysis showed that the RING finger and helix-turn-helix domains of Bmi-1 were required for life span extension and suppression of p16. Furthermore, a RING finger deletion mutant exhibited dominant negative activity, inducing p16 and premature senescence. Interestingly, presenescent cultures of some, but not all, human fibroblasts contained growth-arrested cells expressing high levels of p16 and apparently arrested by a p53- and telomere-independent mechanism. Bmi-1 selectively extended the life span of these cultures. Low O2 concentrations had no effect on p16 levels or life span extension by Bmi-1 but reduce...
Journal of Biological Chemistry, 2002
Genes & Development, 1999
Mechanisms of Development, 1998
The platelet-derived growth factor alpha-receptor (PDGFR-alpha) displays a lineage-specific expre... more The platelet-derived growth factor alpha-receptor (PDGFR-alpha) displays a lineage-specific expression pattern in the mouse embryo and is required for normal development of mesoderm and cephalic neural crest derivatives. The purpose of the present study was to demonstrate the in vivo promoter function of genomic DNA fragments representing the 5'-flanking part of the human PDGFRA gene. 2.2, 0.9 and 0.4 kb PDGFRA promoter fragments, ligated to a lacZ reporter gene, were microinjected into fertilized mouse eggs and transgenic mouse lines were established. The expression patterns were basically similar in the 2.2 and 0.9 kb lines and overlapped grossly the endogenous Pdgfra gene expression pattern. The transgenic line with the highest expression level was chosen for detailed analysis. Expression was, as expected, mainly confined to tissues of mesodermal and neural crest origin. No expression was found in epithelial tissues of endo- or ectodermal origin. The promoter fragments were also active in neuroepithelium and in certain neuronal cell types that did not faithfully express PDGFR-alpha mRNA, while they failed to specify reporter expression in PDGFR-alpha expressing O-2A progenitor cells and other glial elements of the central nervous system. Thus, the isolated human PDGFRA promoter contains most but not all of the regulatory elements that are necessary to establish tissue specific gene expression during development.
These authors contributed equally to this work. Appropriate repair of DNA lesions and the inhibit... more These authors contributed equally to this work. Appropriate repair of DNA lesions and the inhibition of DNA repair activities at telomeres are critical to prevent genomic instability. By fuelling the generation of genetic alterations and by compromising cell viability, genomic instability is a driving force in cancer and aging1, 2. Here we identify MAD2L2 (also known as MAD2B or REV7) through functional genetic screening as a novel factor controlling DNA repair activities at mammalian telomeres. We show that MAD2L2 accumulates at uncapped telomeres and promotes non-homologous end-joining (NHEJ)-mediated fusion of deprotected chromosome ends and genomic instability. MAD2L2 depletion causes elongated 3 ′ telomeric overhangs, implying that MAD2L2 inhibits 5 ′ end-resection. End-resection blocks NHEJ while committing to homology-directed repair (HDR) and is under control of 53BP1, RIF1 and PTIP3. Consistent with MAD2L2 promoting NHEJ-mediated telomere fusion by inhibiting 5 ′ end-resect...
Supplemental Experimental Procedures acetic acid/ethanol fixed slides using antibody JC8 (Abcam) ... more Supplemental Experimental Procedures acetic acid/ethanol fixed slides using antibody JC8 (Abcam) as de-scribed [S10]. Whole cell lysates were prepared in RIPA lysis buffer (150 mM NaCl, 1 % NP40, 0.1 % SDS, 0.5 % DOC, 50 mM Tris-HclRetroviral Infections pH 8, 2 mM EDTA pH 8, 0.2 mM PMSF, 0.5 mM DTT) and equalIMR90 primary human fibroblasts and amphotropic phoenix retrovi-amounts of protein were fractionated on SDS-PAGE and blottedral producer cells (both fromATCC) were grown in DMEMwith 100 U onto nitrocellulose. Immunoblotting was according to standardof penicillin, 0.1 mg/ml streptomycin, 2 mM L-glutamine, 0.1 mM methods using enhanced chemiluminescence (ECL kit Amersham).non-essential amino acids and 15 % FBS (10 % FBS for phoenix). Membranes were blocked overnight at 4C in 5 % milk/0.1 % TweenFor production of retroviral stocks, phoenix cells were seeded at in PBS, primary and secondary antibody incubations were in 1%3 106 cells/10 cm dish and transfected using CaPO4 precipitati...
This article cites 67 articles, 37 of which you can access for free at:
Cancer Research, Aug 15, 2002
The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs... more The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs). One of the key early events in tumorigenic transformation is the ability of cells to overcome replicative senescence. However, the precise genetic changes that are responsible for this event in MECs is largely unknown. Here, we report that Bmi-1, originally identified as a c-Myc cooperating oncoprotein, can bypass senescence, extend the replicative life span, and immortalize MECs. Furthermore, Bmi-1 was overexpressed in immortal MECs and several breast cancer cell lines. Overexpression of Bmi-1 in MECs led to activation of human telomerase reverse transcriptase (hTERT) transcription and induction of telomerase activity. Telomerase induction by Bmi-1 was an early event in the extension of the replicative life span and immortalization. Bmi-1 was not overexpressed in hTERT-immortalized MECs, suggesting that Bmi-1 functions upstream of hTERT. Although, c-Myc has been reported to induce te...
Cancer research, 2002
The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs... more The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs). One of the key early events in tumorigenic transformation is the ability of cells to overcome replicative senescence. However, the precise genetic changes that are responsible for this event in MECs is largely unknown. Here, we report that Bmi-1, originally identified as a c-Myc cooperating oncoprotein, can bypass senescence, extend the replicative life span, and immortalize MECs. Furthermore, Bmi-1 was overexpressed in immortal MECs and several breast cancer cell lines. Overexpression of Bmi-1 in MECs led to activation of human telomerase reverse transcriptase (hTERT) transcription and induction of telomerase activity. Telomerase induction by Bmi-1 was an early event in the extension of the replicative life span and immortalization. Bmi-1 was not overexpressed in hTERT-immortalized MECs, suggesting that Bmi-1 functions upstream of hTERT. Although, c-Myc has been reported to induce te...
1 homologous recombination in BRCA1-null cells 2 3 Harveer Dev, Ting-Wei Will Chiang, Chloe Lesca... more 1 homologous recombination in BRCA1-null cells 2 3 Harveer Dev, Ting-Wei Will Chiang, Chloe Lescale, Inge de Krijger, Alistair G. 4 Martin, Domenic Pilger, Julia Coates, Matylda Sczaniecka-Clift, Wenming Wei, Matthias 5 Ostermaier, Mareike Herzog, Jonathan Lam, Abigail Shea, Mukerrem Demir, Qian Wu, 6 Fengtang Yang, Beiyuan Fu, Zhongwu Lai, Gabriel Balmus, Rimma Belotserkovskaya, 7 Violeta Serra, Mark J. O’Connor, Alejandra Bruna, Petra Beli, Luca Pellegrini, Carlos 8 Caldas, Ludovic Deriano, Jacqueline J.L. Jacobs, Yaron Galanty and Stephen P. 9 Jackson 10 11 The Wellcome Trust/Cancer Research UK Gurdon Institute and Department of 12 Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK. Academic Urology 13 Group, Department of Surgery, Cambridge University Hospitals NHS Foundation Trust, 14 Addenbrooke’s Hospital, Hills Road, Cambridge CB2 0QQ, UK. Genome Integrity, 15 Immunity and Cancer Unit, Department of Immunology, Department of Genomes and 16 Genetics, Institut Pasteu...
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Nature Communications
MAD2L2 (REV7) plays an important role in DNA double-strand break repair. As a member of the shiel... more MAD2L2 (REV7) plays an important role in DNA double-strand break repair. As a member of the shieldin complex, consisting of MAD2L2, SHLD1, SHLD2 and SHLD3, it controls DNA repair pathway choice by counteracting DNA end-resection. Here we investigated the requirements for shieldin complex assembly and activity. Besides a dimerization-surface, HORMA-domain protein MAD2L2 has the extraordinary ability to wrap its C-terminus around SHLD3, likely creating a very stable complex. We show that appropriate function of MAD2L2 within shieldin requires its dimerization, mediated by SHLD2 and accelerating MAD2L2-SHLD3 interaction. Dimerization-defective MAD2L2 impairs shieldin assembly and fails to promote NHEJ. Moreover, MAD2L2 dimerization, along with the presence of SHLD3, allows shieldin to interact with the TRIP13 ATPase, known to drive topological switches in HORMA-domain proteins. We find that appropriate levels of TRIP13 are important for proper shieldin (dis)assembly and activity in DNA...
Molecular & Cellular Proteomics
Loss of telomere protection: consequences and
Nature Communications
Protection of stalled replication forks is essential to prevent genome instability, a major drivi... more Protection of stalled replication forks is essential to prevent genome instability, a major driving force of tumorigenesis. Several key regulators of DNA double-stranded break (DSB) repair, including 53BP1 and RIF1, have been implicated in fork protection. MAD2L2, also known as REV7, plays an important role downstream of 53BP1/RIF1 by counteracting resection at DSBs in the recently discovered shieldin complex. The ability to bind and counteract resection at exposed DNA ends at DSBs makes MAD2L2/shieldin a prime candidate for also suppressing nucleolytic processing at stalled replication forks. However, the function of MAD2L2/shieldin outside of DNA repair is unknown. Here we address this by using genetic and single-molecule analyses and find that MAD2L2 is required for protecting and restarting stalled replication forks. MAD2L2 loss leads to uncontrolled MRE11-dependent resection of stalled forks and single-stranded DNA accumulation, which causes irreparable genomic damage. Unexpect...
Lazzerini Denchi for discussion. J.J. gratefully acknowledges discussion with Maarten van Lohuize... more Lazzerini Denchi for discussion. J.J. gratefully acknowledges discussion with Maarten van Lohuizen and Anton Berns. Work on the telomere damage response in the de Lange lab is supported by a grant from the NIH (AG16642). J.J. was supported by a Dutch Cancer Society Fellowship. Perspective p16INK4a as a Second Effector of the Telomere Damage Pathway Telomere damage resulting from telomere shortening can potentially suppress tumori-genesis by permanently arresting or eliminating incipient cancer cells. Dysfunctional telomeres activate the canonical DNA damage response pathway, resulting in a p53-mediated G1/S arrest and senescence or apoptosis. Experimental induction of telomere damage through inhibition of the telomeric protein TRF2 recapitulates aspects of telomere attrition, including a p53-mediated cell cycle arrest. Using this system, we have shown
This article cites 67 articles, 31 of which can be accessed free
Nucleus (Austin, Tex.), 2012
DNA repair activities at DNA double-strand breaks (DSBs) are under control of regulatory ubiquity... more DNA repair activities at DNA double-strand breaks (DSBs) are under control of regulatory ubiquitylation events governed by the RNF8 and RNF168 ubiquitin-ligases. Defects in this regulatory mechanism, as with mutation of other key DNA damage-response factors, lead to genomic instability and cancer, presumably due to impaired repair of DNA lesions. Recent work revealed that RNF8 and RNF168 also play critical roles at natural chromosome ends, when no longer adequately shielded by telomeres. In contrast to repair of DSBs being needed to maintain genome integrity, repair activities at telomeres create chromosome end-to-end fusions that threaten genome integrity. Upon cell division these telomere fusions give rise to genomic alterations and instability via chromosomal missegregration and initiation of breakage-fusion-bridge cycles. Here, I discuss the role of RNF8 at natural chromosome ends and its (potential) consequences.
Nature Cell Biology, 2011
Molecular and Cellular Biology, 2003
The polycomb protein Bmi-1 represses the INK4a locus, which encodes the tumor suppressors p16 and... more The polycomb protein Bmi-1 represses the INK4a locus, which encodes the tumor suppressors p16 and p14ARF. Here we report that Bmi-1 is downregulated when WI-38 human fibroblasts undergo replicative senescence, but not quiescence, and extends replicative life span when overexpressed. Life span extension by Bmi-1 required the pRb, but not p53, tumor suppressor protein. Deletion analysis showed that the RING finger and helix-turn-helix domains of Bmi-1 were required for life span extension and suppression of p16. Furthermore, a RING finger deletion mutant exhibited dominant negative activity, inducing p16 and premature senescence. Interestingly, presenescent cultures of some, but not all, human fibroblasts contained growth-arrested cells expressing high levels of p16 and apparently arrested by a p53- and telomere-independent mechanism. Bmi-1 selectively extended the life span of these cultures. Low O2 concentrations had no effect on p16 levels or life span extension by Bmi-1 but reduce...
Journal of Biological Chemistry, 2002
Genes & Development, 1999
Mechanisms of Development, 1998
The platelet-derived growth factor alpha-receptor (PDGFR-alpha) displays a lineage-specific expre... more The platelet-derived growth factor alpha-receptor (PDGFR-alpha) displays a lineage-specific expression pattern in the mouse embryo and is required for normal development of mesoderm and cephalic neural crest derivatives. The purpose of the present study was to demonstrate the in vivo promoter function of genomic DNA fragments representing the 5'-flanking part of the human PDGFRA gene. 2.2, 0.9 and 0.4 kb PDGFRA promoter fragments, ligated to a lacZ reporter gene, were microinjected into fertilized mouse eggs and transgenic mouse lines were established. The expression patterns were basically similar in the 2.2 and 0.9 kb lines and overlapped grossly the endogenous Pdgfra gene expression pattern. The transgenic line with the highest expression level was chosen for detailed analysis. Expression was, as expected, mainly confined to tissues of mesodermal and neural crest origin. No expression was found in epithelial tissues of endo- or ectodermal origin. The promoter fragments were also active in neuroepithelium and in certain neuronal cell types that did not faithfully express PDGFR-alpha mRNA, while they failed to specify reporter expression in PDGFR-alpha expressing O-2A progenitor cells and other glial elements of the central nervous system. Thus, the isolated human PDGFRA promoter contains most but not all of the regulatory elements that are necessary to establish tissue specific gene expression during development.
These authors contributed equally to this work. Appropriate repair of DNA lesions and the inhibit... more These authors contributed equally to this work. Appropriate repair of DNA lesions and the inhibition of DNA repair activities at telomeres are critical to prevent genomic instability. By fuelling the generation of genetic alterations and by compromising cell viability, genomic instability is a driving force in cancer and aging1, 2. Here we identify MAD2L2 (also known as MAD2B or REV7) through functional genetic screening as a novel factor controlling DNA repair activities at mammalian telomeres. We show that MAD2L2 accumulates at uncapped telomeres and promotes non-homologous end-joining (NHEJ)-mediated fusion of deprotected chromosome ends and genomic instability. MAD2L2 depletion causes elongated 3 ′ telomeric overhangs, implying that MAD2L2 inhibits 5 ′ end-resection. End-resection blocks NHEJ while committing to homology-directed repair (HDR) and is under control of 53BP1, RIF1 and PTIP3. Consistent with MAD2L2 promoting NHEJ-mediated telomere fusion by inhibiting 5 ′ end-resect...
Supplemental Experimental Procedures acetic acid/ethanol fixed slides using antibody JC8 (Abcam) ... more Supplemental Experimental Procedures acetic acid/ethanol fixed slides using antibody JC8 (Abcam) as de-scribed [S10]. Whole cell lysates were prepared in RIPA lysis buffer (150 mM NaCl, 1 % NP40, 0.1 % SDS, 0.5 % DOC, 50 mM Tris-HclRetroviral Infections pH 8, 2 mM EDTA pH 8, 0.2 mM PMSF, 0.5 mM DTT) and equalIMR90 primary human fibroblasts and amphotropic phoenix retrovi-amounts of protein were fractionated on SDS-PAGE and blottedral producer cells (both fromATCC) were grown in DMEMwith 100 U onto nitrocellulose. Immunoblotting was according to standardof penicillin, 0.1 mg/ml streptomycin, 2 mM L-glutamine, 0.1 mM methods using enhanced chemiluminescence (ECL kit Amersham).non-essential amino acids and 15 % FBS (10 % FBS for phoenix). Membranes were blocked overnight at 4C in 5 % milk/0.1 % TweenFor production of retroviral stocks, phoenix cells were seeded at in PBS, primary and secondary antibody incubations were in 1%3 106 cells/10 cm dish and transfected using CaPO4 precipitati...
This article cites 67 articles, 37 of which you can access for free at:
Cancer Research, Aug 15, 2002
The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs... more The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs). One of the key early events in tumorigenic transformation is the ability of cells to overcome replicative senescence. However, the precise genetic changes that are responsible for this event in MECs is largely unknown. Here, we report that Bmi-1, originally identified as a c-Myc cooperating oncoprotein, can bypass senescence, extend the replicative life span, and immortalize MECs. Furthermore, Bmi-1 was overexpressed in immortal MECs and several breast cancer cell lines. Overexpression of Bmi-1 in MECs led to activation of human telomerase reverse transcriptase (hTERT) transcription and induction of telomerase activity. Telomerase induction by Bmi-1 was an early event in the extension of the replicative life span and immortalization. Bmi-1 was not overexpressed in hTERT-immortalized MECs, suggesting that Bmi-1 functions upstream of hTERT. Although, c-Myc has been reported to induce te...
Cancer research, 2002
The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs... more The vast majority of breast cancers are carcinomas that arise from mammary epithelial cells (MECs). One of the key early events in tumorigenic transformation is the ability of cells to overcome replicative senescence. However, the precise genetic changes that are responsible for this event in MECs is largely unknown. Here, we report that Bmi-1, originally identified as a c-Myc cooperating oncoprotein, can bypass senescence, extend the replicative life span, and immortalize MECs. Furthermore, Bmi-1 was overexpressed in immortal MECs and several breast cancer cell lines. Overexpression of Bmi-1 in MECs led to activation of human telomerase reverse transcriptase (hTERT) transcription and induction of telomerase activity. Telomerase induction by Bmi-1 was an early event in the extension of the replicative life span and immortalization. Bmi-1 was not overexpressed in hTERT-immortalized MECs, suggesting that Bmi-1 functions upstream of hTERT. Although, c-Myc has been reported to induce te...
1 homologous recombination in BRCA1-null cells 2 3 Harveer Dev, Ting-Wei Will Chiang, Chloe Lesca... more 1 homologous recombination in BRCA1-null cells 2 3 Harveer Dev, Ting-Wei Will Chiang, Chloe Lescale, Inge de Krijger, Alistair G. 4 Martin, Domenic Pilger, Julia Coates, Matylda Sczaniecka-Clift, Wenming Wei, Matthias 5 Ostermaier, Mareike Herzog, Jonathan Lam, Abigail Shea, Mukerrem Demir, Qian Wu, 6 Fengtang Yang, Beiyuan Fu, Zhongwu Lai, Gabriel Balmus, Rimma Belotserkovskaya, 7 Violeta Serra, Mark J. O’Connor, Alejandra Bruna, Petra Beli, Luca Pellegrini, Carlos 8 Caldas, Ludovic Deriano, Jacqueline J.L. Jacobs, Yaron Galanty and Stephen P. 9 Jackson 10 11 The Wellcome Trust/Cancer Research UK Gurdon Institute and Department of 12 Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK. Academic Urology 13 Group, Department of Surgery, Cambridge University Hospitals NHS Foundation Trust, 14 Addenbrooke’s Hospital, Hills Road, Cambridge CB2 0QQ, UK. Genome Integrity, 15 Immunity and Cancer Unit, Department of Immunology, Department of Genomes and 16 Genetics, Institut Pasteu...
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Nature Communications
MAD2L2 (REV7) plays an important role in DNA double-strand break repair. As a member of the shiel... more MAD2L2 (REV7) plays an important role in DNA double-strand break repair. As a member of the shieldin complex, consisting of MAD2L2, SHLD1, SHLD2 and SHLD3, it controls DNA repair pathway choice by counteracting DNA end-resection. Here we investigated the requirements for shieldin complex assembly and activity. Besides a dimerization-surface, HORMA-domain protein MAD2L2 has the extraordinary ability to wrap its C-terminus around SHLD3, likely creating a very stable complex. We show that appropriate function of MAD2L2 within shieldin requires its dimerization, mediated by SHLD2 and accelerating MAD2L2-SHLD3 interaction. Dimerization-defective MAD2L2 impairs shieldin assembly and fails to promote NHEJ. Moreover, MAD2L2 dimerization, along with the presence of SHLD3, allows shieldin to interact with the TRIP13 ATPase, known to drive topological switches in HORMA-domain proteins. We find that appropriate levels of TRIP13 are important for proper shieldin (dis)assembly and activity in DNA...