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DNA double-strand breaks (DSBs) pose a serious threat to genomic stability. Paradoxically, hundreds of programed DSBs are generated by SPO11 in meiotic prophase, which are exclusively repaired by homologous recombination (HR) to promote obligate crossover between homologous chromosomes. In somatic cells, MRE11-RAD50-NBS1 (MRN) complex-dependent DNA end resection is a prerequisite for HR repair, especially for DSBs that are covalently linked with proteins or chemicals. Interestingly, all meiotic DSBs are linked with SPO11 after being generated. Although MRN complex’s function in meiotic DSB repair has been established in lower organisms, the role of MRN complex in mammalian meiotic DSB repair is not clear. Here, we show that MRN complex is essential for repairing meiotic SPO11-linked DSBs in male mice. In male germ cells, conditional inactivation of NBS1, a key component of MRN complex, causes dramatic reduction of DNA end resection and defective HR repair in meiotic prophase. NBS1 loss severely disrupts chromosome synapsis, generates abnormal chromosome structures, and eventually leads to meiotic arrest and male infertility in mice. Unlike in somatic cells, the recruitment of NBS1 to SPO11-linked DSB sites is MDC1-independent but requires other phosphorylated proteins. Collectively, our study not only reveals the significance of MRN complex in repairing meiotic DSBs but also discovers a unique mechanism that recruits MRN complex to SPO11-linked DSB sites.

As an important player in DNA damage response, BRCA1 maintains genomic stability and suppresses tumorigenesis by promoting DNA double-strand break (DSB) repair through homologous recombination (HR). Since the cloning of BRCA1 gene, many Brca1 mutant alleles have been generated in mice. Mice carrying homozygous Brca1 mutant alleles are embryonic lethal, suggesting that BRCA1’s functions are important for embryonic development. Studies of embryonic development in Brca1 mutant mice not only reveal the physiological significance of BRCA1’s known function in HR, but also lead to the discovery of BRCA1’s new function in HR: regulation of DSB repair pathway choice.

BRCA1 is critical for DNA double-strand break (DSB) repair by homologous recombination (HR). BRCA1 deficient mice are embryonic lethal. Previous studies have shown that 53BP1 knockout (KO) rescues embryonic lethality of BRCA1 hypomorphic mutant mice by restoring HR. Here, we show that 53BP1 KO can partially rescue embryonic lethality of BRCA1 total KO mice, but HR is not restored in BRCA1-53BP1 double knockout (DKO) mice. As a result, BRCA1-53BP1 DKO cells are extremely sensitive to PARP inhibitors (PARPi). In addition to HR deficiency, BRCA1-53BP1 DKO cells have elevated microhomology-mediated end joining (MMEJ) activity and G2/M cell cycle checkpoint defects, causing severe genomic instability in these cells. Interestingly, BRCA1-53BP1 DKO mice rapidly develop thymic lymphoma that is 100% penetrant, which is not observed in any BRCA1 mutant mice rescued by 53BP1 KO. Taken together, our study reveals that 53BP1 KO can partially rescue embryonic lethality caused by complete BRCA1 loss without rescuing HR-related defects. This finding suggests that loss of 53BP1 can support the development of cancers with silenced BRCA1 expression without causing PARPi resistance.

The systematic design of functional peptides has technological and therapeutic applications. However, there is a need for pattern-based search engines that help locate desired functional motifs in primary sequences regardless of their evolutionary conservation. Existing databases such as The Protein Secondary Structure database (PSS) no longer serves the community, while the Dictionary of Protein Secondary Structure (DSSP) annotates the secondary structures when tertiary structures of proteins are provided. Here, we extract 1.7 million helices from the PDB and compile them into a database (Therapeutic Peptide Design database; TP-DB) that allows queries of compounded patterns to facilitate the identification of sequence motifs of helical structures. We show how TP-DB helps us identify a known purification-tag-specific antibody that can be repurposed into a diagnostic kit for Helicobacter pylori . We also show how the database can be used to design a new antimicrobial peptide that shows better Candida albicans clearance and lower hemolysis than its template homologs. Finally, we demonstrate how TP-DB can suggest point mutations in helical peptide blockers to prevent a targeted tumorigenic protein-protein interaction. TP-DB is made available at http://dyn.life.nthu.edu.tw/design/ . Here, we present TP-DB; a pattern-based search engine based on 1.67 million helices from the Protein Database (PDB). We demonstrate the utility of TP-DB in identifying microbe-specific antigens, as well as the design of antimicrobial peptides and Protein-protein interaction blockers.

Chromosome synapsis is an evolutionarily conserved process essential for meiotic recombination. HORMAD1 and HORMAD2, which monitor chromosome asynapsis by localizing to unsynapsed chromosome axes, are removed from synapsed chromosome axes by TRIP13, though the biological significance of this process remains unclear. We show that when HORMAD1 and HORMAD2 are retained on synapsed chromosome axes, they recruit BRCA1, activate chromosome asynapsis checkpoint, and trigger oocyte elimination. Unexpectedly, N-terminal tagging retains HORMAD1 and HORMAD2 on synapsed chromosome axes without triggering oocyte elimination due to defective BRCA1 recruitment. Mechanistically, HORMAD1 co-immunoprecipitates with BRCA1 readily, not through the canonical closure motif-binding mode but via an interface on its HORMA domain near the N-terminus. HORMAD2 co-immunoprecipitates with BRCA1 weakly but also regulates its recruitment. Collectively, the TRIP13-dependent removal of HORMAD1 and HORMAD2 from synapsed chromosome axes is essential for female fertility, preventing aberrant chromosome asynapsis checkpoint activation and unintended oocyte elimination. Chromosome synapsis is an essential process during meiotic recombination and gametogenesis. Here they show that TRIP13-dependent removal of HORMAD1 and HORMAD2 from synapsed chromosome axes during meiotic prophase is crucial for female fertility, as it prevents aberrant chromosome asynapsis checkpoint activation and unintended oocyte elimination.

HORMAD1 is a meiosis-specific protein that promotes synapsis and recombination of homologous chromosomes in meiotic prophase. Originally identified as a cancer/testis antigen, HORMAD1 is also aberrantly expressed in several cancers. However, the functions of HORMAD1 in cancer cells are still not clear. Here, we show that HORMAD1 is aberrantly expressed in a wide variety of cancers and compromises DNA mismatch repair in cancer cells. Mechanistically, HORMAD1 interacts with MCM8–MCM9 complex and prevents its efficient nuclear localization. As a consequence, HORMAD1-expressing cancer cells have reduced MLH1 chromatin binding and DNA mismatch repair defects. Consistently, HORMAD1 expression is associated with increased mutation load and genomic instability in many cancers. Taken together, our study provides mechanistic insights into HORMAD1’s functions in cancer cells, which can potentially be exploited for targeted therapy of HORMAD1-expressing cancers.

Photoinduced dearomatization of arenes is a powerful strategy in organic synthesis to disrupt the stable aromaticity; however, the asymmetric dearomatization photocatalysis of unactivated arenes remains highly challenging and rare. Herein we demonstrate an enzyme-mimicking cage-confined visible-light asymmetric photocatalysis method for intramolecular dearomative cycloaddition with electron-deficient β -aryl enones. Owing to the multi-functional synergy of chirality, energy transfer, and host-guest interactions in the confined microenvironments, the self-assembled chiral cage-photoreactor could pre-organize the arenes and activate the β -aryl enones to give stereoselectively fused cyclobutanes through visible-light induced [2 + 2] ortho -cycloaddition. Notably, the competing transformation to stable [4 + 2] cycloadducts has been inhibited, producing thermodynamically unfavorable [2 + 2] cycloadducts with excellent regio-, diastereo-, and enantioselectivities. The asymmetric dearomatization photocatalysis of unactivated arenes remains challenging and rare. Herein the authors demonstrate an enzyme‐mimicking cage‐confined visible‐light asymmetric photocatalysis method for intramolecular dearomative cycloaddition with electron‐deficient β‐aryl enones.

In the meiotic prophase, programmed SPO11‐linked DNA double‐strand breaks (DSBs) are repaired by homologous recombination (HR). The MRE11‐RAD50‐NBS1 (MRN) complex is essential for initiating DNA end resection, the first step of HR. However, residual DNA end resection still occurs in Nbs1 knockout (KO) spermatocytes for unknown reasons. Here, we show that DNA end resection is completely abolished in Mre11 KO spermatocytes. In addition, Mre11 KO, but not Nbs1 KO, undifferentiated spermatogonia are rapidly exhausted due to DSB accumulation, proliferation defects, and elevated apoptosis. Cellular studies reveal that a small amount of MRE11 retained in the nucleus of Nbs1 KO cells likely underlies the differences between Mre11 and Nbs1 KO cells. Taken together, our study not only demonstrates an irreplaceable role of the MRE11 in DNA end resection at SPO11‐linked DSBs but also unveils a unique function of MRE11 in maintaining the long‐term viability of undifferentiated spermatogonia. The MRE11‐RAD50‐NBS1 (MRN) complex in the nucleus initiates DNA end resection at double‐strand break (DSB) sites and supports the long‐term viability of undifferentiated spermatogonia in mice. In the absence of NBS1, a small amount of intact MRE11‐RAD50 complex can still localise to the nucleus and can promote residual DNA end resection to keep the long‐term viability of undifferentiated spermatogonia. However, in the absence of MRE11, DNA end resection is completely abolished and undifferentiated spermatogonia are rapid exhausted due to DSB accumulation and apoptosis.

Hypothyroidism is associated with anxiety and depression. However, the mechanisms underlying these neuropsychiatric symptoms remain largely unknown. This study aimed to investigate the role of the NLRP1 inflammasome in anxiety-like behavior in mice with hypothyroidism. Male C57BL/6j mice were divided into three groups: euthyroid controls, a hypothyroid model group induced by propylthiouracil, and a hypothyroid group treated with levothyroxine (L-T4). Anxiety-like behavior was assessed using both the open field test and the elevated plus maze. Protein levels of NLRP1 inflammasome components and associated cytokines in the hippocampus were examined by Western blot analysis. Mice with hypothyroidism exhibited anxiety-like behavior, as evidenced by decreased activity in the central area of the open field and reduced time spent in the open arms of the elevated plus maze. These behavioral changes were accompanied by an increased expression of NLRP1 inflammasome components (NLRP1, ASC, and Caspase-1) and associated cytokines (IL-1β, IL-18, and IL-6) in the hippocampus. L-T4 treatment reversed both the behavioral deficits and inflammatory changes. Our findings highlight the crucial role of NLRP1 inflammasome activation in the hippocampus in mediating anxiety-like behavior in hypothyroid mice, shedding light on the mechanisms underlying hypothyroidism-related psychiatric comorbidities and identifying potential therapeutic targets.

This study evaluated and compared the functional recovery and histopathological outcomes of treatment involving low-intensity pulsed ultrasound (LIPUS) and methylcobalamin (B12) on brachial plexus injury (BPI) in an experimental rat model. Three days after BPI, the rats were assigned to receive either LIPUS or methylcobalamin alone or in combination consecutively for 12 days. Serial changes in sensory and motor behavioral responses, as well as morphological and immunohistochemical changes for substance P (SP), ionized calcium-binding adapter molecule 1 (iba1), brain-derived neurotrophic factor (BDNF), and S100 were examined 28 days after BPI as the outcome measurements. Early intervention of LIPUS and methylcobalamin, whether alone or in combination, augmented the sensory and motor behavioral recovery as well as modulated SP and iba1 expression in spinal dorsal horns, BDNF, and S100 in the injured nerve. Moreover, the combined therapy with its synergistic effect gave the most beneficial effect in accelerating functional recovery. In view of the effective initiation of early recovery of sensory and motor functions, treatment with LIPUS and methylcobalamin in combination has a potential role in the clinical management of early-phase BPI.