Biology subjects

Jantsch, V.

Publications and source records attributed to Jantsch, V..

11 recordsLinked to original sources

bioRxiv2026

CIP2A tetramerization is required for mitotic DNA repair

DNA lesions that persist in mitosis threaten genome stability. These lesions recruit TOPBP1-CIP2A, a complex crucial to tether and process damaged DNA on mitotic chromosomes. Importantly, CIP2A is synthetic lethal in BRCA1/2 mutant cancer cells. However, mechanistic insight into the function of CIP2A is lacking. Here we provide first structural insights into full-length CIP2A and reveal how CIP2A dimers, 46 nm in length, assemble via conserved C-terminal motifs into dumbbell-like tetramers. DNA repair signatures demonstrate that CIP2A tetramerization is crucial for mitotic DNA repair by polymerase theta (POLQ). Tetramerization of CIP2A is needed to recruit POLQ to mitotic DNA lesions and to prevent micronucleation upon replication-born DNA lesions. Tetramerization-defective CIP2A mutants specifically decrease survival of BRCA1/2 mutant cancer cells in a dominant negative manner. Combined, we demonstrate that CIP2A tetramers are crucial components of a mitotic DNA-tethering and repair scaffold, which processes replication-mediated DNA lesions that persist in mitosis.

cell biology↗

bioRxiv2026

ZHP-2/HEI10 generates CO precursors and triggers procrossover factor coarsening and CO formation through Polo kinase recruitment

During meiosis, programmed DNA double-strand breaks (DSBs) are repaired with the homolog to form crossovers (COs) essential for chromosome segregation, or noncrossovers (nCOs) to restore genomic integrity. Only a few recombination intermediates will become COs and these sites are progressively enriched in proCO factors at the expense of nCO sites, referred to as coarsening. Here, we show that in C. elegans this process is engineered by ZHP-2/HEI10, a conserved E3 ligase that has functions at early and late stages of CO formation. Early on, ZHP-2-mediated loss of RMH-1/RMI1 and HIM-6/BLM from strand exchange intermediates is required for joint molecule formation and nCO repair. In zhp-2 mutants, proCO factors accumulate at HR sites, leading to defects in CO formation and CO spacing. We find that Polo kinase recruitment to a ZHP-2 at CO precursors signals an end to further DSB formation, and triggers proCO factor coarsening and CO formation. We propose that ZHP-2 disassembles proCO factors from recombination intermediates until it is inactivated at CO precursors through Polo kinase recruitment, leading to stabilization of proCO factors, and resolution of joint molecules as crossovers. Our study reveals that ZHP-2/HEI10 is the central component of a Polo kinase-driven switch that initiates proCO factor coarsening and execution of crossing over.

cell biology↗

bioRxiv2026

BRC-2/BRCA2-RIPR-1 mediated constraints on homologous recombination execution are spatiotemporally regulated during meiosis

Homologous recombination-dependent processing of meiotic double-strand breaks is crucial to generate functional gametes. The breast and ovarian cancer susceptibility gene BRCA2 is essential for the loading of RAD51-DMC1 recombinases at DNA breaks to allow accurate repair. Here, we identify the novel protein RIPR-1 as a binding partner of Caenorhabditis elegans BRC-2/BRCA2. RIPR-1 and BRC-2 form an obligate complex both in vitro and in vivo and display interdependent loading in developing oocytes. Loss of ripr-1 results in the complete destabilization of BRC-2, while brc-2 is only partially required to preserve RIPR-1 stability. Strikingly, we found a dramatic accumulation of RAD-51 in late pachytene cells of both ripr-1 and brc-2 nulls, unveiling a BRCA2-independent pathway for recruitment of RAD-51 at resected meiotic DNA breaks. RIPR-1 enhances BRC-2 binding to single-stranded DNA and unlike the individual components, the assembled RIPR-1-BRC-2 complex can also bind double-stranded DNA in vitro. Surprisingly, we observe that RAD-51-dependent crossover designation still occurs in absence of RIPR-1-BRC-2, indicating partial, and stage-dependent constraints on homologous recombination execution. Altogether, our work identifies a novel BRC-2 interactor and sheds new light on HR-mediated regulation of DNA repair during meiosis.

Cell Biology↗

bioRxiv2026

Dbf4-dependent kinase promotes meiotic DNA end resection through cyclin-dependent kinase 12 and DNA-2 in Caenorhabditis elegans

Meiotic crossovers depend on the accurate processing of programmed DNA double-strand breaks by homologous recombination, which involves generating by resection the single-stranded DNA ends required for the subsequent strand invasion step. How regulatory kinases control DNA end resection in animal meiosis remains poorly understood. Here, we identify the Caenorhabditis elegans Dbf4-dependent kinase (DDK) complex, composed of CDC-7 and DBF-4, and identify CDK-12 as a candidate substrate. DDK promotes efficient meiotic DNA end resection, while crossover formation remains largely preserved in its absence. Loss of DDK function leads to SPO-11-dependent chromosome bridges at diakinesis that arise from recombination intermediates formed early in recombination. In addition to chromosome bridges, we observed elevated heterologous recombination that occurs independently of the canonical or alternative end-joining pathways. Interestingly, CDC-7 and DBF-4 localize dynamically during prophase I and load onto DNA in a hierarchical manner that depends on the BRC-1-BRD-1 complex. Epistasis analysis placed CDC-7 and CDK-12 within the DNA-2-dependent branch of long-range DNA resection. Together, our findings reveal an unidentified DDK/CDK-12/DNA-2 signaling axis that promotes efficient meiotic DNA resection to avoid the generation of aberrant recombination outcomes.

cell biology↗

bioRxiv2026

A DIA-based quantitative crosslinking mass spectrometryframework for dynamic structural proteomics

Proteins undergo dynamic conformational rearrangements and interactions that are central to their biological functions. Quantitative crosslinking mass spectrometry enables the analysis of those dynamics and molecular interactions, but rigorous confidence assessment and empirical validation strategies for quantitative measurements remain underdeveloped, and integrated analysis of complementary structural features, including monolinks and protein-RNA adducts, remains limited. Here we present a data-independent acquisition (DIA)-based framework for quantitative crosslinking mass spectrometry (DIA-QCLMS) that combines optimized acquisition strategies, crosslink-aware spectral libraries and empirical false-discovery-rate (FDR) validation. The workflow supports crosslinks, monolinks and protein-RNA adducts and integrates spectral-library generation from two crosslinking search engines (xiSEARCH and MS Annika). To enable robust confidence assessment in DIA data, we developed a four-state target-decoy spectral library strategy that explicitly models target-target, target-decoy, decoy-target and decoy-decoy crosslink spectra. Experimental entrapment datasets enabled empirical validation of confidence estimation, whereas benchmarking with PhoX-crosslinked Cas9 demonstrated improved quantitative completeness and reproducibility compared with data-dependent acquisition. Application of the workflow to the ATP-dependent RNA helicase UAP56 (DDX39B) resolved ligand-dependent changes in intramolecular restraints, residue accessibility and candidate RNA-contact sites associated with the transition from an open to a clamped conformation. These results establish DIA-QCLMS as a scalable framework for quantitative structural proteomics and provide practical strategies for confidence-controlled analysis of dynamic protein interactions and conformational states.

biochemistry↗

bioRxiv2024

Distinct intersecting pathways link homolog pairing to initiation of meiotic chromosome synapsis

Faithful meiotic segregation requires pairwise alignment of the homologous chromosomes and Synaptonemal Complex assembly (SC) at their interface. Here, we investigate on new factors that promote and coordinate these events during C. elegans meiosis. We identify BRA-2 (BMP Receptor Associated family member 2) as an interactor of HIM-17, previously shown to promote double-strand break formation. We found that loss of bra-2 specifically impairs synapsis licensing without affecting homologs recognition, SC maintenance or chromosome movement. Double mutant analysis revealed a previously unrecognized role for HIM-17 in promoting homolog pairing under dysfunctional SC assembly, without perturbing nuclear envelope recruitment of factors required for chromosome movement. We provide evidence that bra-2 and him-17 act in distinct pathways, exerting partially redundant functions in SC licensing, as well as separable roles in regulating homologs pairing. Altogether, our findings unveil novel mechanisms that ensure stabilization of homologous chromosome interaction via SC licensing upon homology assessment.

cell biology↗

bioRxiv2021

The CHK-2 antagonizing phosphatase PPM-1.D regulates meiotic entry via catalytic and non-catalytic activities

The transition from the stem cell/progenitor fate to meiosis is mediated by several redundant post-transcriptional regulatory pathways in C. elegans. Interfering with all three branches causes tumorous germlines. SCFPROM-1 comprises one branch and mediates a scheduled degradation step at entry into meiosis. prom-1 mutants show defects in timely initiation of events of meiotic prophase I, resulting in high rates of embryonic lethality. Here, we identify the phosphatase PPM-1.D/Wip1 as crucial substrate for PROM-1. We report that PPM-1.D antagonizes CHK-2 kinase, a key regulator for meiotic prophase initiation e.g., DNA double strand breaks, chromosome pairing and synaptonemal complex formation. We propose that PPM-1.D controls the amount of active CHK-2 by both catalytic and non-catalytic activities, where strikingly the non-catalytic regulation seems to be crucial at meiotic entry. PPM-1.D sequesters CHK-2 at the nuclear periphery and programmed SCFPROM-1 mediated degradation of PPM-1.D liberates the kinase and promotes meiotic entry.

cell biology↗

bioRxiv2020

Poly(ADP-ribose) glycohydrolase promotes formation and homology-directed repair of meiotic DNA double-strand breaks independent of its catalytic activity

Poly(ADP-ribosyl)ation is a reversible post-translational modification synthetized by ADP-ribose transferases and removed by poly(ADP-ribose) glycohydrolase (PARG), which plays important roles in DNA damage repair. While well-studied in somatic tissues, much less is known about poly(ADP-ribosyl)ation in the germline, where DNA double-strand breaks are introduced by a regulated program and repaired by crossover recombination to establish a tether between homologous chromosomes. The interaction between the parental chromosomes is facilitated by meiotic specific adaptation of the chromosome axes and cohesins, and reinforced by the synaptonemal complex. Here, we uncover an unexpected role for PARG in promoting the induction of meiotic DNA breaks and their homologous recombination-mediated repair in Caenorhabditis elegans. PARG-1/PARG interacts with both axial and central elements of the synaptonemal complex, REC-8/Rec8 and the MRN/X complex. PARG-1 shapes the recombination landscape and reinforces the tightly regulated control of crossover numbers without requiring its catalytic activity. We unravel roles in regulating meiosis, beyond its enzymatic activity in poly(ADP-ribose) catabolism.

developmental biology↗

bioRxiv2018

The BRCA1-BARD1 complex associates with the synaptonemal complex and pro-crossover factors and influences RAD-51 dynamics during Caenorhabditis elegans meiosis

During meiosis, the maternal and paternal homologous chromosomes must align along their entire length and recombine to achieve faithful segregation in the gametes. Meiotic recombination is accomplished through the formation of DNA double-strand breaks, a subset of which can mature into crossovers to link the parental homologous chromosomes and promote their segregation. Breast and ovarian cancer susceptibility protein BRCA1 and its heterodimeric partner BARD1 play a pivotal role in DNA repair in mitotic cells; however, their functions in gametogenesis are less well understood. Here we show that localization of BRC-1 and BRD-1 (Caenorhabditis elegans orthologues of BRCA1 and BARD1) is dynamic during meiotic prophase I; they ultimately becoming concentrated at regions surrounding the presumptive crossover sites, co-localizing with the pro-crossover factors COSA-1, MSH-5 and ZHP-3. The synaptonemal complex is essential for BRC-1 loading onto chromosomes but recombination is not. BRC-1 forms an in vivo complex with the synaptonemal complex component SYP-3 and the crossover-promoting factor MSH-5. Furthermore, BRC-1 is essential for efficient stage-specific recruitment of the RAD-51 recombinase to DNA damage sites when synapsis is impaired and upon induction of exogenous DNA double-strand breaks. Taken together, our data provide new insights into the localization and meiotic function of the BRC-1-BRD-1 complex and highlight their essential role in DNA double-strand break repair during gametogenesis.\n\nAuthor summarySexually reproducing species rely on meiosis to transmit their genetic information across generations. Parental chromosomes (homologues) undergo many distinctive processes in their complex journey from attachment to segregation. The physiological induction of DNA double strand breaks is crucial for promoting correct chromosome segregation: they are needed to activate the DNA repair machinery responsible for creating physical connections, or crossovers (COs), between the homologues. In turn, crossovers promote the accurate segregation of the chromosomes in daughter cells. The BRCA1-BARD1 complex has a pivotal role during DNA repair in somatic cells and is exclusively located on unaligned chromosomal regions during mammalian meiosis. We show that in Caenorhabditis elegans, BRCA1 and BARD1 localize to chromosomes at all stages of meiotic prophase I and are enriched at presumptive crossover sites. We found that BRCA1 promotes DNA loading of the repair factor RAD-51 in specific mutant backgrounds and upon exogenous damage induction. Our data provide evidence for a direct physical association between BRCA1 and pro-crossover factors (including the synaptonemal complex) and identify an important role for BRCA1 in stimulating meiotic DNA repair. Further studies are necessary to identify the substrates acted upon by BRCA1-BARD1 complex to maintain genome stability in the gametes.

genetics↗

bioRxiv2017

The conserved LEM-3/Ankle1 nuclease is involved in the combinatorial regulation of meiotic recombination repair and chromosome segregation in Caenorhabditis elegans

Homologous recombination is essential for crossover (CO) formation and accurate chromosome segregation during meiosis. It is of considerable importance to work out how recombination intermediates are processed leading to CO and non-crossover (NCO) outcome. Genetic analysis in budding yeast and Caenorhabditis elegans indicates that the processing of meiotic recombination intermediates involves a combination of nucleases and DNA repair enzymes. We previously reported that in C. elegans meiotic Holiday junction resolution is mediated by two redundant pathways, conferred by the SLX-1 and MUS-81 nucleases, and by the HIM-6 Blooms helicase in conjunction with the XPF-1 endonucleases, respectively. Both pathways require the scaffold protein SLX-4. However, in the absence of all these enzymes residual processing of meiotic recombination intermediates still occurs and CO formation is reduced but not abolished. Here we show that the LEM-3 nuclease, mutation of which by itself does not have an overt meiotic phenotype, genetically interacts with slx-1 and mus-81 mutants, the respective double mutants leading to 100% embryonic lethality. LEM-3 and MUS-81 act redundantly, their combined loss leading to a reduced number of early meiotic recombination intermediates, to a delayed disassembly of foci associated with CO designated sites, and to the formation of univalents linked by SPO-11 dependent chromatin bridges (dissociated bivalents). However, LEM-3 foci do not co-localize with ZHP-3 a marker that congresses into CO designated sites. In addition, neither CO frequency nor distribution is altered in lem-3 single mutants or in combination with mus-81 or slx-4 mutations, indicating that LEM-3 drives NCO outcome. Finally, we found persistent chromatin bridges during meiotic divisions in lem-3; slx-4 double mutants. Supported by the localization of LEM-3 between dividing meiotic nuclei, this data suggests that LEM-3 is able to process erroneous recombination intermediates that persist into the second meiotic divisions.\n\nAuthor SummaryMeiotic recombination is required for genetic diversity and for the proper chromosome segregation. Recombination intermediates, such as Holliday junctions (HJs), are generated and eventually resolved to produce crossover (CO) and non-crossover (NCO). While an excess of meiotic double-strand breaks is generated, most breaks are repaired without leading to a CO outcome and usually only one break for each chromosome pair matures into a CO-designated site in Caenorhabditis elegans. Resolution of meiotic recombination intermediates and CO formation have been reported to be highly regulated by several structure-specific endonucleases and the Bloom helicase. However, little is known about enzymes involved in the NCO recombination intermediate resolution. In this study, we found that a conserved nuclease LEM-3/Ankle1 acts in parallel to the SLX-1/MUS-81 pathway to process meiotic recombination intermediates. Mutation of lem-3 has no effect on CO frequency and distribution, indicating LEM-3 functions as a nuclease promoting NCO outcome. Interestingly, a prominent localization of LEM-3 is found between dividing meiotic nuclei. We provide evidence that LEM-3 is also involved in processing remaining, erroneous recombination intermediates during meiotic divisions.

cell biology↗

bioRxiv2017

LEM-3 is a midbody-tethered DNA nuclease that resolves chromatin bridges during cytokinesis

Faithful chromosome segregation and genome maintenance requires the removal of all DNA bridges that physically link chromosomes before cells divide. Using C. elegans embryos we show that the LEM-3/Ankle1 nuclease defines a new genome integrity mechanism by processing DNA bridges right before cells divide. LEM-3 acts at the midbody, the structure where abscission occurs at the end of cytokinesis. LEM-3 localization depends on factors needed for midbody assembly, and LEM-3 accumulation is increased and prolonged when chromatin bridges are trapped at the cleavage plane. LEM-3 locally processes chromatin bridges that arise from incomplete DNA replication, unresolved recombination intermediates or the perturbance of chromosome structure. Proper LEM-3 midbody localization and function is regulated by AIR-2/Aurora B kinase. Strikingly, LEM-3 act cooperatively with the BRC-1/BRCA1 homologous recombination factor to promote genome integrity. These findings provide a molecular basis for the suspected role of the LEM-3 orthologue Ankle1 in human breast cancer.

cell biology↗