Thyroid hormone receptor interacting protein 13 (TRIP13) AAA-ATPase is a novel mitotic checkpoint-silencing protein

Targeting of oncogenic AAA-ATPase TRIP13 reduces progression of pancreatic ductal adenocarcinoma

Thyroid hormone receptor-interacting protein 13 (TRIP13) is involved in cancer progression, but its role in pancreatic ductal adenocarcinoma (PDAC) is unknown. Thus, we assessed the expression, functional role, and mechanism of action of TRIP13 in PDAC. We further examined the efficacy of TRIP13 inhibitor, DCZ0415, alone or in combination with gemcitabine on malignant phenotypes, tumor progression, and immune response. We found that TRIP13 was overexpressed in human PDACs relative to corresponding normal pancreatic tissues. TRIP13 knockdown or treatment of PDAC cells with DCZ0415 reduced proliferation and colony formation, and induced G2/M cell cycle arrest and apoptosis. Additionally, TRIP13 knockdown or targeting with DCZ0415 reduced the migration and invasion of PDAC cells by increasing E-cadherin and decreasing N-cadherin and vimentin. Pharmacologic targeting or silencing of TRIP13 also resulted in reduce expression of FGFR4 and STAT3 phosphorylation, and downregulation of the Wnt/β-catenin pathway. In immunocompromised mouse models of PDAC, knockdown of TRIP13 or treatment with DCZ0415 reduced tumor growth and metastasis. In an immunocompetent syngeneic PDAC model, DCZ0415 treatment enhanced the immune response by lowering expression of PD1/PDL1, increasing granzyme B/perforin expression, and facilitating infiltration of CD3/CD4 T-cells. Further, DCZ0415 potentiated the anti-metastatic and anti-tumorigenic activities of gemcitabine by reducing proliferation and angiogenesis and by inducing apoptosis and the immune response. These preclinical findings show that TRIP13 is involved in PDAC progression and targeting of TRIP13 augments the anticancer effect of gemcitabine.

The role of the HORMA domain proteins ATG13 and ATG101 in initiating autophagosome biogenesis

Autophagy is a process of regulated degradation. It eliminates damaged and unnecessary cellular components by engulfing them with a de novo-generated organelle: the double-membrane autophagosome. The past three decades have provided us with a detailed parts list of the autophagy initiation machinery, have developed important insights into how these processes function and have identified regulatory proteins. It is now clear that autophagosome biogenesis requires the timely assembly of a complex machinery. However, it is unclear how a putative stable machine is assembled and disassembled and how the different parts cooperate to perform its overall function. Although they have long been somewhat enigmatic in their precise role, HORMA domain proteins (first identified in Hop1p, Rev7p and MAD2 proteins) autophagy-related protein 13 (ATG13) and ATG101 of the ULK-kinase complex have emerged as important coordinators of the autophagy-initiating subcomplexes. Here, we will particularly focus on ATG13 and ATG101 and the role of their unusual metamorphosis in initiating autophagosome biogenesis. We will also explore how this metamorphosis could potentially be purposefully rate-limiting and speculate on how it could regulate the spontaneous self-assembly of the autophagy-initiating machinery.

TI17, a novel compound, exerts anti-MM activity by impairing Trip13 function of DSBs repair and enhancing DNA damage

BACKGROUND

Thyroid hormone receptor interacting protein 13 (Trip13) is an AAA-ATPase that regulates the assembly or disassembly protein complexes and mediates Double-strand breaks (DSBs) repair. Overexpression of Trip13 has been detected in many cancers and is associated with myeloma progression, disease relapse and poor prognosis inmultiple myeloma (MM).

METHODS

We have identified a small molecular, TI17, through a parallel compound-centric approach, which specifically targets Trip13. To identify whether TI17 targeted Trip13, pull-down and nuclear magnetic resonance spectroscopy (NMR) assays were performed. Cell counting kit-8, clone formation, apoptosis and cell cycle assays were applied to investigate the effects of TI17. We also utilized a mouse model to investigate the effects of TI17 in vivo.

RESULTS

TI17 effectively inhibited the proliferation of MM cells, and induced the cycle arrest and apoptosis of MM cells. Furthermore, treatment with TI17 abrogates tumor growth and has no apparent side effects in mouse xenograft models. TI17 specifically impaired Trip13 function of DSBs repair and enhanced DNA damage responses in MM. Combining with melphalan or HDAC inhibitor panobinostat triggers synergistic anti-MM effect.

CONCLUSIONS

Our study suggests that TI17 could be acted as a specific inhibitor of Trip13 and supports a preclinical proof of concept for therapeutic targeting of Trip13 in MM.

Targeting TRIP13 for overcoming anticancer drug resistance (Review)

Cancer is one of the greatest dangers to human wellbeing and survival. A key barrier to effective cancer therapy is development of resistance to anti‑cancer medications. In cancer cells, the AAA+ ATPase family member thyroid hormone receptor interactor 13 (TRIP13) is key in promoting treatment resistance. Nonetheless, knowledge of the molecular processes underlying TRIP13‑based resistance to anticancer therapies is lacking. The present study evaluated the function of TRIP13 expression in anticancer drug resistance and potential methods to overcome this resistance. Additionally, the underlying mechanisms by which TRIP13 promotes resistance to anticancer drugs were explored, including induction of mitotic checkpoint complex surveillance system malfunction, promotion of DNA repair, the enhancement of autophagy and the prevention of immunological clearance. The effects of combination treatment, which include a TRIP13 inhibitor in addition to other inhibitors, were discussed. The present study evaluated the literature on TRIP13 as a possible target and its association with anticancer drug resistance, which may facilitate improvements in current anticancer therapeutic options.

Exportin-mediated nucleocytoplasmic transport maintains Pch2 homeostasis during meiosis

The meiotic recombination checkpoint reinforces the order of events during meiotic prophase I, ensuring the accurate distribution of chromosomes to the gametes. The AAA+ ATPase Pch2 remodels the Hop1 axial protein enabling adequate levels of Hop1-T318 phosphorylation to support the ensuing checkpoint response. While these events are localized at chromosome axes, the checkpoint activating function of Pch2 relies on its cytoplasmic population. In contrast, forced nuclear accumulation of Pch2 leads to checkpoint inactivation. Here, we reveal the mechanism by which Pch2 travels from the cell nucleus to the cytoplasm to maintain Pch2 cellular homeostasis. Leptomycin B treatment provokes the nuclear accumulation of Pch2, indicating that its nucleocytoplasmic transport is mediated by the Crm1 exportin recognizing proteins containing Nuclear Export Signals (NESs). Consistently, leptomycin B leads to checkpoint inactivation and impaired Hop1 axial localization. Pch2 nucleocytoplasmic traffic is independent of its association with Zip1 and Orc1. We also identify a functional NES in the non-catalytic N-terminal domain of Pch2 that is required for its nucleocytoplasmic trafficking and proper checkpoint activity. In sum, we unveil another layer of control of Pch2 function during meiosis involving nuclear export via the exportin pathway that is crucial to maintain the critical balance of Pch2 distribution among different cellular compartments.

Oncogenic Targets Regulated by Tumor-Suppressive miR-30c-1-3p and miR-30c-2-3p: TRIP13 Facilitates Cancer Cell Aggressiveness in Breast Cancer

Accumulating evidence suggests that the miR-30 family act as critical players (tumor-suppressor or oncogenic) in a wide range of human cancers. Analysis of microRNA (miRNA) expression signatures and The Cancer Genome Atlas (TCGA) database revealed that that two passenger strand miRNAs, miR-30c-1-3p and miR-30c-2-3p, were downregulated in cancer tissues, and their low expression was closely associated with worse prognosis in patients with BrCa. Functional assays showed that miR-30c-1-3p and miR-30c-2-3p overexpression significantly inhibited cancer cell aggressiveness, suggesting these two miRNAs acted as tumor-suppressors in BrCa cells. Notably, involvement of passenger strands of miRNAs is a new concept of cancer research. Further analyses showed that seven genes (TRIP13, CCNB1, RAD51, PSPH, CENPN, KPNA2, and MXRA5) were putative targets of miR-30c-1-3p and miR-30c-2-3p in BrCa cells. Expression of seven genes were upregulated in BrCa tissues and predicted a worse prognosis of the patients. Among these genes, we focused on TRIP13 and investigated the functional significance of this gene in BrCa cells. Luciferase reporter assays showed that TRIP13 was directly regulated by these two miRNAs. TRIP13 knockdown using siRNA attenuated BrCa cell aggressiveness. Inactivation of TRIP13 using a specific inhibitor prevented the malignant transformation of BrCa cells. Exploring the molecular networks controlled by miRNAs, including passenger strands, will facilitate the identification of diagnostic markers and therapeutic target molecules in BrCa.

Genetic variants underlying developmental arrests in human preimplantation embryos

Developmental arrest in preimplantation embryos is one of the major causes of assisted reproduction failure. It is briefly defined as a delay or a failure of embryonic development in producing viable embryos during ART cycles. Permanent or partial developmental arrest can be observed in the human embryos from one-cell to blastocyst stages. These arrests mainly arise from different molecular biological defects, including epigenetic disturbances, ART processes, and genetic variants. Embryonic arrests were found to be associated with a number of variants in the genes playing key roles in embryonic genome activation, mitotic divisions, subcortical maternal complex formation, maternal mRNA clearance, repairing DNA damage, transcriptional, and translational controls. In this review, the biological impacts of these variants are comprehensively evaluated in the light of existing studies. The creation of diagnostic gene panels and potential ways of preventing developmental arrests to obtain competent embryos are also discussed.

Biallelic variants in MAD2L1BP (p31comet) cause female infertility characterized by oocyte maturation arrest

Human oocyte maturation arrest represents one of the severe conditions for female patients with primary infertility. However, the genetic factors underlying this human disease remain largely unknown. The spindle assembly checkpoint (SAC) is an intricate surveillance mechanism that ensures accurate segregation of chromosomes throughout cell cycles. Once the kinetochores of chromosomes are correctly attached to bipolar spindles and the SAC is satisfied, the MAD2L1BP, best known as p31comet, binds mitosis arrest deficient 2 (MAD2) and recruits the AAA+-ATPase TRIP13 to disassemble the mitotic checkpoint complex (MCC), leading to the cell-cycle progression. In this study, by whole-exome sequencing (WES), we identified homozygous and compound heterozygous MAD2L1BP variants in three families with female patients diagnosed with primary infertility owing to oocyte metaphase I (MI) arrest. Functional studies revealed that the protein variants resulting from the C-terminal truncation of MAD2L1BP lost their binding ability to MAD2. cRNA microinjection of full-length or truncated MAD2L1BP uncovered their discordant roles in driving the extrusion of polar body 1 (PB1) in mouse oocytes. Furthermore, the patient's oocytes carrying the mutated MAD2L1BP resumed polar body extrusion (PBE) when rescued by microinjection of full-length MAD2L1BP cRNAs. Together, our studies identified and characterized novel biallelic variants in MAD2L1BP responsible for human oocyte maturation arrest at MI, and thus prompted new therapeutic avenues for curing female primary infertility.

The conserved AAA ATPase PCH-2 distributes its regulation of meiotic prophase events through multiple meiotic HORMADs in C. elegans

During meiotic prophase, the essential events of homolog pairing, synapsis, and recombination are coordinated with meiotic progression to promote fidelity and prevent aneuploidy. The conserved AAA+ ATPase PCH-2 coordinates these events to guarantee crossover assurance and accurate chromosome segregation. How PCH-2 accomplishes this coordination is poorly understood. Here, we provide evidence that PCH-2 decelerates pairing, synapsis and recombination in C. elegans by remodeling meiotic HORMADs. We propose that PCH-2 converts the closed versions of these proteins, which drive these meiotic prophase events, to unbuckled conformations, destabilizing interhomolog interactions and delaying meiotic progression. Further, we find that PCH-2 distributes this regulation among three essential meiotic HORMADs in C. elegans: PCH-2 acts through HTP-3 to regulate pairing and synapsis, HIM-3 to promote crossover assurance, and HTP-1 to control meiotic progression. In addition to identifying a molecular mechanism for how PCH-2 regulates interhomolog interactions, our results provide a possible explanation for the expansion of the meiotic HORMAD family as a conserved evolutionary feature of meiosis. Taken together, our work demonstrates that PCH-2's remodeling of meiotic HORMADs has functional consequences for the rate and fidelity of homolog pairing, synapsis, recombination and meiotic progression, ensuring accurate meiotic chromosome segregation.

Antinuclear antibodies in individuals with COVID-19 reflect underlying disease: Identification of new autoantibodies in systemic sclerosis (CDK9) and malignancy (RNF20, RCC1, TRIP13)

A high prevalence of antinuclear antibodies (ANA) in COVID-19 has been insinuated, but the nature of the target antigens is poorly understood. We studied ANA by indirect immunofluorescence in 229 individuals with COVID-19. The target antigens of high titer ANA (≥1:320) were determined by immunoprecipitation (IP) combined with liquid-chromatography-mass spectrometry (MS). High titer ANA (≥1:320) were found in 14 (6%) of the individuals with COVID-19. Of the 14 COVID-19 cases with high titer ANA, 6 had an underlying autoimmune disease and 5 a malignancy. IP-MS revealed known target antigens associated with autoimmune disease as well as novel autoantigens, including CDK9 (in systemic sclerosis) and RNF20, RCC1 and TRIP13 (in malignancy). The novel autoantigens were confirmed by IP-Western blotting. In conclusion, in depth analysis of the targets of high titer ANA revealed novel autoantigens in systemic sclerosis and in malignant disease.

Principles and dynamics of spindle assembly checkpoint signalling

The transmission of a complete set of chromosomes to daughter cells during cell division is vital for development and tissue homeostasis. The spindle assembly checkpoint (SAC) ensures correct segregation by informing the cell cycle machinery of potential errors in the interactions of chromosomes with spindle microtubules prior to anaphase. To do so, the SAC monitors microtubule engagement by specialized structures known as kinetochores and integrates local mechanical and chemical cues such that it can signal in a sensitive, responsive and robust manner. In this Review, we discuss how SAC proteins interact to allow production of the mitotic checkpoint complex (MCC) that halts anaphase progression by inhibiting the anaphase-promoting complex/cyclosome (APC/C). We highlight recent advances aimed at understanding the dynamic signalling properties of the SAC and how it interprets various naturally occurring intermediate attachment states. Further, we discuss SAC signalling in the context of the mammalian multisite kinetochore and address the impact of the fibrous corona. We also identify current challenges in understanding how the SAC ensures high-fidelity chromosome segregation.

Dynamics and regulation of mitotic chromatin accessibility bookmarking at single-cell resolution

Although mitotic chromosomes are highly compacted and transcriptionally inert, some active chromatin features are retained during mitosis to ensure the proper postmitotic reestablishment of maternal transcriptional programs, a phenomenon termed "mitotic bookmarking." However, the dynamics and regulation of mitotic bookmarking have not been systemically surveyed. Using single-cell transposase-accessible chromatin sequencing (scATAC-seq), we examined 6538 mitotic L02 human liver cells of variable stages and found that chromatin accessibility remained changing throughout cell division, with a constant decrease until metaphase and a gradual increase as chromosomes segregated. In particular, a subset of chromatin regions were identified to remain open throughout mitosis, and genes associated with these bookmarked regions are primarily linked to rapid reactivation upon mitotic exit. We also demonstrated that nuclear transcription factor Y subunit α (NF-YA) preferentially occupied bookmarked regions and contributed to transcriptional reactivation after mitosis. Our study uncovers the dynamic and regulatory blueprint of mitotic bookmarking.

Meiotic defects in human oocytes: Potential causes and clinical implications

Meiotic defects cause abnormal chromosome segregation leading to aneuploidy in mammalian oocytes. Chromosome segregation is particularly error-prone in human oocytes, but the mechanisms behind such errors remain unclear. To explain the frequent chromosome segregation errors, recent investigations have identified multiple meiotic defects and explained how these defects occur in female meiosis. In particular, we review the causes of cohesin exhaustion, leaky spindle assembly checkpoint (SAC), inherently unstable meiotic spindle, fragmented kinetochores or centromeres, abnormal aurora kinases (AURK), and clinical genetic variants in human oocytes. We mainly focus on meiotic defects in human oocytes, but also refer to the potential defects of female meiosis in mouse models.

Trip13 Depletion in Liver Cancer Induces a Lipogenic Response Contributing to Plin2-Dependent Mitotic Cell Death

Aberrant energy metabolism and cell cycle regulation both critically contribute to malignant cell growth and both processes represent targets for anticancer therapy. It is shown here that depletion of the AAA+-ATPase thyroid hormone receptor interacting protein 13 (Trip13) results in mitotic cell death through a combined mechanism linking lipid metabolism to aberrant mitosis. Diminished Trip13 levels in hepatocellular carcinoma cells result in insulin-receptor-/Akt-pathway-dependent accumulation of lipid droplets, which act as functional acentriolar microtubule organizing centers disturbing mitotic spindle polarity. Specifically, the lipid-droplet-coating protein perilipin 2 (Plin2) is required for multipolar spindle formation, induction of DNA damage, and mitotic cell death. Plin2 expression in different tumor cells confers susceptibility to cell death induced by Trip13 depletion as well as treatment with paclitaxel, a spindle-interfering drug commonly used against different cancers. Thus, assessment of Plin2 levels enables the stratification of tumor responsiveness to mitosis-targeting drugs, including clinically approved paclitaxel and Trip13 inhibitors currently under development.

Recovery from spindle checkpoint-mediated arrest requires a novel Dnt1-dependent APC/C activation mechanism

The activated spindle assembly checkpoint (SAC) potently inhibits the anaphase-promoting complex/cyclosome (APC/C) to ensure accurate chromosome segregation at anaphase. Early studies have recognized that the SAC should be silenced within minutes to enable rapid APC/C activation and synchronous segregation of chromosomes once all kinetochores are properly attached, but the underlying silencers are still being elucidated. Here, we report that the timely silencing of SAC in fission yeast requires dnt1+, which causes severe thiabendazole (TBZ) sensitivity and increased rate of lagging chromosomes when deleted. The absence of Dnt1 results in prolonged inhibitory binding of mitotic checkpoint complex (MCC) to APC/C and attenuated protein levels of Slp1Cdc20, consequently slows the degradation of cyclin B and securin, and eventually delays anaphase entry in cells released from SAC activation. Interestingly, Dnt1 physically associates with APC/C upon SAC activation. We propose that this association may fend off excessive and prolonged MCC binding to APC/C and help to maintain Slp1Cdc20 stability. This may allow a subset of APC/C to retain activity, which ensures rapid anaphase onset and mitotic exit once SAC is inactivated. Therefore, our study uncovered a new player in dictating the timing and efficacy of APC/C activation, which is actively required for maintaining cell viability upon recovery from the inhibition of APC/C by spindle checkpoint.

MiR-129-5p/TRIP13 affects malignant phenotypes of colorectal cancer cells

OBJECTIVE

Aberrant miR-129-5p expression is a key modulator of cancer development. But how the miRNA affects colorectal cancer (CRC) remains unclear. This study was designed to illustrate the underlying mechanism of miR-129-5p in CRC.

METHODS

MiR-129-5p expression at cellular level was assayed by qRT-PCR. Its role in CRC cell phenotypes was studied by cell function experiments. The binding relationship between miR-129-5p and TRIP13 was analyzed and verified by target changed to bioinformatics prediction and dual-luciferase detection. Furthermore, the functional mechanism based on miR-129-5p and TRIP13 in CRC was studied through rescue experiments.

RESULTS

CRC cell lines presented prominently lower miR-129-5p levels than the normal colon epithelial cell line. The forced miR-129-5p level suppressed CRC cell growth. TRIP13 was proved to be a target of miR-129-5p in CRC cells, and miR-129-5p overexpression reduced TRIP13 expression. TRIP13 knockdown resulted in cell cycle arrest. Additionally, TRIP13 overexpression restored the impacts of miR-129-5p overexpression on cell malignant phenotypes and cell cycle.

CONCLUSION

MiR-129-5p down-regulated TRIP13 expression, thereby restraining the malignant progression of CRC cells. The findings may offer a new target for molecular therapy of CRC.

Analysis of the potential role of fission yeast PP2A in spindle assembly checkpoint inactivation

As a surveillance mechanism, the activated spindle assembly checkpoint (SAC) potently inhibits the E3 ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) to ensure accurate chromosome segregation. Although the protein phosphatase 2A (PP2A) has been proposed to be both, directly and indirectly, involved in spindle assembly checkpoint inactivation in mammalian cells, whether it is similarly operating in the fission yeast Schizosaccharomycer pombe has never been demonstrated. Here, we investigated whether fission yeast PP2A is involved in SAC silencing by following the rate of cyclin B (Cdc13) destruction at SPBs during the recovery phase in nda3-KM311 cells released from the inhibition of APC/C by the activated spindle checkpoint. The timing of the SAC inactivation is only slightly delayed when two B56 regulatory subunits (Par1 and Par2) of fission yeast PP2A are absent. Overproduction of individual PP2A subunits either globally in the nda3-KM311 arrest-and-release system or locally in the synthetic spindle checkpoint activation system only slightly suppresses the SAC silencing defects in PP1 deletion (dis2Δ) cells. Our study thus demonstrates that the fission yeast PP2A is not a key regulator actively involved in SAC inactivation.

Identification of Novel Variants of Thyroid Hormone Receptor Interaction Protein 13 That Cause Female Infertility Characterized by Zygotic Cleavage Failure

Zygotic cleavage failure (ZCF) is a severe, early type of embryonic arrest in which zygotes cannot complete the first cleavage. Although mutations in BTG4 and CHEK1 have been identified as genetic causes of ZCF, these genes only explain a small population of ZCF cases. Thus, the underlying genetic causes for other affected individuals need to be identified. Here, we identified three TRIP13 missense variants responsible for ZCF in two patients and showed that they followed a recessive inheritance pattern. All three variants resulted in obvious changes in hydrogen bonding and consistent increase in DNA damage. Additionally, transcriptomic sequencing of oocytes and arrested embryos containing these variants suggested a greater number of differentially expressed transcripts in germinal vesicle (GV) oocytes than in 1-cell embryos. Vital genes for energy metabolism and cell cycle procession were widely and markedly downregulated, while DNA repair-related genes were significantly upregulated in both GV oocytes and 1-cell embryos of patients. These findings highlight a critical role of TRIP13 in meiosis and mitosis, as well as expand the genetic and phenotypic spectra of TR1P13 variants with respect to female infertility, especially in relation to ZCF.

Checkpoint control in meiotic prophase: Idiosyncratic demands require unique characteristics

Chromosomal transactions such as replication, recombination and segregation are monitored by cell cycle checkpoint cascades. These checkpoints ensure the proper execution of processes that are needed for faithful genome inheritance from one cell to the next, and across generations. In meiotic prophase, a specialized checkpoint monitors defining events of meiosis: programmed DNA break formation, followed by dedicated repair through recombination based on interhomolog (IH) crossovers. This checkpoint shares molecular characteristics with canonical DNA damage checkpoints active during somatic cell cycles. However, idiosyncratic requirements of meiotic prophase have introduced unique features in this signaling cascade. In this review, we discuss the unique features of the meiotic prophase checkpoint. While being related to canonical DNA damage checkpoint cascades, the meiotic prophase checkpoint also shows similarities with the spindle assembly checkpoint (SAC) that guards chromosome segregation. We highlight these emerging similarities in the signaling logic of the checkpoints that govern meiotic prophase and chromosome segregation, and how thinking of these similarities can help us better understand meiotic prophase control. We also discuss work showing that, when aberrantly expressed, components of the meiotic prophase checkpoint might alter DNA repair fidelity and chromosome segregation in cancer cells. Considering checkpoint function in light of demands imposed by the special characteristics of meiotic prophase helps us understand checkpoint integration into the meiotic cell cycle machinery.

Inducing Synergistic DNA Damage by TRIP13 and PARP1 Inhibitors Provides a Potential Treatment for Hepatocellular Carcinoma

Thyroid hormone receptor interactor 13 (TRIP13), an AAA-ATPase, participates in the development of many cancers. This study explores the function of TRIP13 and synergistic effects of TRIP13 and PARP1 inhibitors in hepatocellular carcinoma (HCC). The dose-dependent effects of TRIP13 and PARP1 inhibitors on HCC cells proliferation or migration were investigated by the CCK-8 and Transwell assays. Using siRNA or lentivirus to knock down TRIP13, we tested HCC cell and tumor growth in vitro and in vivo. The DNA damage caused by TRIP13 and PARP1 inhibitors was measured by the phosphorylation of H2AX, one of the DNA damage biomarkers. The phosphorylation of H2AX was increased after treatment with DCZ0415 or TRIP13 knockdown. Combining DCZ0415 with PARP1 inhibitor, Olaparib induced synergistic anti-HCC activity. We also found that the overexpression of TRIP13 is significantly associated with early recurrent HCC and poor survival. Up-regulation of TRIP13 in HCC was regulated by transcription factor SP1. In conclusion, our study demonstrated that DCZ0415 targeting TRIP13 impaired non-homologous end-joining repair to inhibit HCC progression and had a synergistic effect with PARP1 inhibitor Olaparib in HCC, suggesting a potential treatment of HCC.

Role of ubiquitin-protein ligase UBR5 in the disassembly of mitotic checkpoint complexes

The mitotic checkpoint system is essential for the prevention of mistakes in the segregation of chromosomes in mitosis. As long as chromosomes are not attached correctly to the mitotic spindle, a mitotic checkpoint complex (MCC) is assembled and inhibits the action of ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) to initiate anaphase. When the checkpoint is turned off, MCC is disassembled, allowing anaphase initiation. The mechanisms of MCC disassembly have been studied, but the regulation of this process remained obscure. We found that a second ubiquitin ligase, UBR5 (ubiquitin-protein ligase N-recognin 5), ubiquitylates MCC components and stimulates the disassembly of MCC from APC/C, as well as the dissociation of a subcomplex of MCC.

The mitotic (or spindle assembly) checkpoint system ensures accurate chromosome segregation in mitosis by preventing the onset of anaphase until correct bipolar attachment of sister chromosomes to the mitotic spindle is attained. It acts by promoting the assembly of a mitotic checkpoint complex (MCC), composed of mitotic checkpoint proteins BubR1, Bub3, Mad2, and Cdc20. MCC binds to and inhibits the action of ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome), which targets for degradation regulators of anaphase initiation. When the checkpoint system is satisfied, MCCs are disassembled, allowing the recovery of APC/C activity and initiation of anaphase. Many of the pathways of the disassembly of the different MCCs have been elucidated, but the mode of their regulation remained unknown. We find that UBR5 (ubiquitin-protein ligase N-recognin 5) is associated with the APC/C*MCC complex immunopurified from extracts of nocodazole-arrested HeLa cells. UBR5 binds to mitotic checkpoint proteins BubR1, Bub3, and Cdc20 and promotes their polyubiquitylation in vitro. The dissociation of a Bub3*BubR1 subcomplex of MCC is stimulated by UBR5-dependent ubiquitylation, as suggested by observations that this process in mitotic extracts requires UBR5 and α−β bond hydrolysis of adenosine triphosphate. Furthermore, a system reconstituted from purified recombinant components carries out UBR5- and ubiquitylation-dependent dissociation of Bub3*BubR1. Immunodepletion of UBR5 from mitotic extracts slows down the release of MCC components from APC/C and prolongs the lag period in the recovery of APC/C activity in the exit from mitotic checkpoint arrest. We suggest that UBR5 may be involved in the regulation of the inactivation of the mitotic checkpoint.

KIF18B promotes breast cancer cell proliferation, migration and invasion by targeting TRIP13 and activating the Wnt/β‑catenin signaling pathway

Kinesin superfamily member 18B (KIF18B) has previously been reported to be upregulated in breast cancer (BC) and is involved in BC tumorigenesis. Therefore, the present study aimed to investigate the effects and underlying mechanisms of KIF18B in BC. Comprehensive bioinformatics analysis was performed, using data from The Cancer Genome Atlas. KIF18B knockdown and thyroid hormone receptor-interacting protein 13 (TRIP13) overexpression in BC cells were induced via transfection, by using the short hairpin RNA-KIF18B and overexpression-TRIP13 vectors, respectively. Cellular processes, including proliferation, migration and invasion were assessed using colony formation, wound healing and Transwell assays, respectively. mRNA and protein expression levels were determined using reverse transcription-quantitative PCR and western blot analysis, respectively. Protein-protein interactions were determined using co-immunoprecipitation. The results demonstrated that the KIF18B expression levels were upregulated in BC, particularly in triple-negative BC (TNBC) tissues and cell lines. KIF18B knockdown inhibited the proliferation, migration and invasion of HCC-1937 TNBC cells. Furthermore, MMP12 and MMP9 protein expression levels were decreased by KIF18B knockdown. TRIP13 expression was also demonstrated to be upregulated in BC, particularly in TNBC tissues and cell lines. TRIP13 expression levels positively correlated with those of KIF18B in BC tissues and cells, and further analysis verified that TRIP13 and KIF14B were able to directly bind to each other. However, TRIP13 overexpression abolished the effects of KIF18B knockdown on HCC-1937 cells. Furthermore, KIF18B knockdown decreased β-catenin, c-Myc and cyclin D1 protein expression levels; however, TRIP13 overexpression resulted in the recovery of all respective protein expression levels. On the whole, the present study demonstrates that KIF18B promotes BC malignant events, including the proliferation, migration and invasion of TNBC cells. These results indicate that KIF18B may play an oncogenic role in BC by upregulating TRIP13 expression, thereby activating the Wnt/β-catenin signaling pathway.

TRIP13, identified as a hub gene of tumor progression, is the target of microRNA-4693-5p and a potential therapeutic target for colorectal cancer

Colorectal cancer (CRC) is one of the digestive tract malignancies whose early symptoms are not obvious. This study aimed to identify novel targets for CRC therapy, especially early-stage CRC, by reanalyzing the publicly available GEO and TCGA databases. Thyroid hormone receptor interactor 13 (TRIP13) correlated with tumor progression and prognosis of patients after several rounds of analysis, including weighted gene correlation network analysis (WGCNA), and further chosen for experimental validation in cancer cell lines and patient samples. We identified that mRNA and protein levels of TRIP13 increased in CRC cells and tumor tissues with tumor progression. miR-4693-5p was significantly downregulated in CRC tumor tissues and bound to the 3′ untranslated region (3′UTR) of TRIP13, downregulating TRIP13 expression. DCZ0415, a small molecule inhibitor targeting TRIP13, induced anti-tumor activity in vitro and in vivo. DCZ0415 markedly suppressed CRC cell proliferation, migration, and tumor growth, promoted cell apoptosis, and resulted in the arrest of the cell cycle. Our research suggests that TRIP13 might play a crucial role in CRC progression and could be a potential target for CRC therapy.

Evolutionary Dynamics and Molecular Mechanisms of HORMA Domain Protein Signaling

Controlled assembly and disassembly of multi-protein complexes is central to cellular signaling. Proteins of the widespread and functionally diverse HORMA family nucleate assembly of signaling complexes by binding short peptide motifs through a distinctive safety-belt mechanism. HORMA proteins are now understood as key signaling proteins across kingdoms, serving as infection sensors in a bacterial immune system and playing central roles in eukaryotic cell cycle, genome stability, sexual reproduction, and cellular homeostasis pathways. Here, we describe how HORMA proteins' unique ability to adopt multiple conformational states underlies their functions in these diverse contexts. We also outline how a dedicated AAA+ ATPase regulator, Pch2/TRIP13, manipulates HORMA proteins' conformational states to activate or inactivate signaling in different cellular contexts. The emergence of Pch2/TRIP13 as a lynchpin for HORMA protein action in multiple genome-maintenance pathways accounts for its frequent misregulation in human cancers and highlights TRIP13 as a novel therapeutic target. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DNA damage is overcome by TRIP13 overexpression during cisplatin nephrotoxicity

Cisplatin is a commonly used chemotherapeutic agent to treat a wide array of cancers that is frequently associated with toxic injury to the kidney due to oxidative DNA damage and perturbations in cell cycle progression leading to cell death. In this study, we investigated whether thyroid receptor interacting protein 13 (TRIP13) plays a central role in the protection of the tubular epithelia following cisplatin treatment by circumventing DNA damage. Following cisplatin treatment, double-stranded DNA repair pathways were inhibited using selective blockers to proteins involved in either homologous recombination or non-homologous end joining. This led to increased blood markers of acute kidney injury (AKI) (creatinine and neutrophil gelatinase–associated lipocalin), tubular damage, activation of DNA damage marker (γ-H2AX), elevated appearance of G2/M blockade (phosphorylated histone H3 Ser10 and cyclin B1), and apoptosis (cleaved caspase-3). Conditional proximal tubule–expressing Trip13 mice were observed to be virtually protected from the cisplatin nephrotoxicity by restoring most of the pathological phenotypes back toward normal conditions. Our findings suggest that TRIP13 could circumvent DNA damage in the proximal tubules during cisplatin injury and that TRIP13 may constitute a new therapeutic target in protecting the kidney from nephrotoxicants and reduce outcomes leading to AKI.

Evolutionary Dynamics of the Spindle Assembly Checkpoint in Eukaryotes

The tremendous diversity in eukaryotic life forms can ultimately be traced back to evolutionary modifications at the level of molecular networks. Deep understanding of these modifications will not only explain cellular diversity, but will also uncover different ways to execute similar processes and expose the evolutionary 'rules' that shape the molecular networks. Here, we review the evolutionary dynamics of the spindle assembly checkpoint (SAC), a signaling network that guards fidelity of chromosome segregation. We illustrate how the interpretation of divergent SAC systems in eukaryotic species is facilitated by combining detailed molecular knowledge of the SAC and extensive comparative genome analyses. Ultimately, expanding this to other core cellular systems and experimentally interrogating such systems in organisms from all major lineages may start outlining the routes to and eventual manifestation of the cellular diversity of eukaryotic life.

Molecular mechanisms of assembly and TRIP13-mediated remodeling of the human Shieldin complex

The Shieldin complex, composed of REV7, SHLD1, SHLD2, and SHLD3, protects DNA double-strand breaks (DSBs) to promote nonhomologous end joining. The AAA⁺ ATPase TRIP13 remodels Shieldin to regulate DNA repair pathway choice. Here we report crystal structures of human SHLD3-REV7 binary and fused SHLD2-SHLD3-REV7 ternary complexes, revealing that assembly of Shieldin requires fused SHLD2-SHLD3 induced conformational heterodimerization of open (O-REV7) and closed (C-REV7) forms of REV7. We also report the cryogenic electron microscopy (cryo-EM) structures of the ATPγS-bound fused SHLD2-SHLD3-REV7-TRIP13 complexes, uncovering the principles underlying the TRIP13-mediated disassembly mechanism of the Shieldin complex. We demonstrate that the N terminus of REV7 inserts into the central channel of TRIP13, setting the stage for pulling the unfolded N-terminal peptide of C-REV7 through the central TRIP13 hexameric channel. The primary interface involves contacts between the safety-belt segment of C-REV7 and a conserved and negatively charged loop of TRIP13. This process is mediated by ATP hydrolysis-triggered rotatory motions of the TRIP13 ATPase, thereby resulting in the disassembly of the Shieldin complex.

Chromosomal instability by mutations in the novel minor spliceosome component CENATAC

Aneuploidy is the leading cause of miscarriage and congenital birth defects, and a hallmark of cancer. Despite this strong association with human disease, the genetic causes of aneuploidy remain largely unknown. Through exome sequencing of patients with constitutional mosaic aneuploidy, we identified biallelic truncating mutations in CENATAC (CCDC84). We show that CENATAC is a novel component of the minor (U12-dependent) spliceosome that promotes splicing of a specific, rare minor intron subtype. This subtype is characterized by AT-AN splice sites and relatively high basal levels of intron retention. CENATAC depletion or expression of disease mutants resulted in excessive retention of AT-AN minor introns in ˜ 100 genes enriched for nucleocytoplasmic transport and cell cycle regulators, and caused chromosome segregation errors. Our findings reveal selectivity in minor intron splicing and suggest a link between minor spliceosome defects and constitutional aneuploidy in humans.

The RAS GTPase RIT1 compromises mitotic fidelity through spindle assembly checkpoint suppression

The spindle assembly checkpoint (SAC) functions as a sensor of unattached kinetochores that delays mitotic progression into anaphase until proper chromosome segregation is guaranteed.^1,2 Disruptions to this safety mechanism lead to genomic instability and aneuploidy, which serve as the genetic cause of embryonic demise, congenital birth defects, intellectual disability, and cancer.^3,4 However, despite the understanding of the fundamental mechanisms that control the SAC, it remains unknown how signaling pathways directly interact with and regulate the mitotic checkpoint activity. In response to extracellular stimuli, a diverse network of signaling pathways involved in cell growth, survival, and differentiation are activated, and this process is prominently regulated by the Ras family of small guanosine triphosphatases (GTPases).⁵ Here we show that RIT1, a Ras-related GTPase that regulates cell survival and stress response,⁶ is essential for timely progression through mitosis and proper chromosome segregation. RIT1 dissociates from the plasma membrane (PM) during mitosis and interacts directly with SAC proteins MAD2 and p31^comet in a process that is regulated by cyclin-dependent kinase 1 (CDK1) activity. Furthermore, pathogenic levels of RIT1 silence the SAC and accelerate transit through mitosis by sequestering MAD2 from the mitotic checkpoint complex (MCC). Moreover, SAC suppression by pathogenic RIT1 promotes chromosome segregation errors and aneuploidy. Our results highlight a unique function of RIT1 compared to other Ras GTPases and elucidate a direct link between a signaling pathway and the SAC through a novel regulatory mechanism.

Intricate Regulatory Mechanisms of the Anaphase-Promoting Complex/Cyclosome and Its Role in Chromatin Regulation

The ubiquitin (Ub)-proteasome system is vital to nearly every biological process in eukaryotes. Specifically, the conjugation of Ub to target proteins by Ub ligases, such as the Anaphase-Promoting Complex/Cyclosome (APC/C), is paramount for cell cycle transitions as it leads to the irreversible destruction of cell cycle regulators by the proteasome. Through this activity, the RING Ub ligase APC/C governs mitosis, G1, and numerous aspects of neurobiology. Pioneering cryo-EM, biochemical reconstitution, and cell-based studies have illuminated many aspects of the conformational dynamics of this large, multi-subunit complex and the sophisticated regulation of APC/C function. More recent studies have revealed new mechanisms that selectively dictate APC/C activity and explore additional pathways that are controlled by APC/C-mediated ubiquitination, including an intimate relationship with chromatin regulation. These tasks go beyond the traditional cell cycle role historically ascribed to the APC/C. Here, we review these novel findings, examine the mechanistic implications of APC/C regulation, and discuss the role of the APC/C in previously unappreciated signaling pathways.

Clinical Significance and Systematic Expression Analysis of the Thyroid Receptor Interacting Protein 13 (TRIP13) as Human Gliomas Biomarker

The prognosis of malignant gliomas such as glioblastoma multiforme (GBM) has remained poor due to limited therapeutic strategies. Thus, it is pivotal to determine prognostic factors for gliomas. Thyroid Receptor Interacting Protein 13 (TRIP13) was found to be overexpressed in several solid tumors, but its role and clinical significance in gliomas is still unclear. Here, we conducted a comprehensive expression analysis of TRIP13 to determine the prognostic values. Gene expression profiles of the Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA) and GSE16011 dataset showed increased TRIP13 expression in advanced stage and worse prognosis in IDH-wild type lower-grade glioma. We performed RT-PCR and Western blot to validate TRIP13 mRNA expression and protein levels in GBM cell lines. TRIP13 co-expressed genes via database screening were regulated by essential cancer-related upstream regulators (such as TP53 and FOXM1). Then, TCGA analysis revealed that more TRIP13 promoter hypomethylation was observed in GBM than in low-grade glioma. We also inferred that the upregulated TRIP13 levels in gliomas could be regulated by dysfunction of miR-29 in gliomas patient cohorts. Moreover, TRIP13-expressing tumors not only had higher aneuploidy but also tended to reduce the ratio of CD8⁺/Treg, which led to a worse survival outcome. Overall, these findings demonstrate that TRIP13 has with multiple functions in gliomas, and they may be crucial for therapeutic potential.

State changes of the HORMA protein ASY1 are mediated by an interplay between its closure motif and PCH2

HORMA domain-containing proteins (HORMADs) play an essential role in meiosis in many organisms. The meiotic HORMADs, including yeast Hop1, mouse HORMAD1 and HORMAD2, and Arabidopsis ASY1, assemble along chromosomes at early prophase and the closure motif at their C-termini has been hypothesized to be instrumental for this step by promoting HORMAD oligomerization. In late prophase, ASY1 and its homologs are progressively removed from synapsed chromosomes promoting chromosome synapsis and recombination. The conserved AAA+ ATPase PCH2/TRIP13 has been intensively studied for its role in removing HORMADs from synapsed chromosomes. In contrast, not much is known about how HORMADs are loaded onto chromosomes. Here, we reveal that the PCH2-mediated dissociation of the HORMA domain of ASY1 from its closure motif is important for the nuclear targeting and subsequent chromosomal loading of ASY1. This indicates that the promotion of ASY1 to an ‘unlocked’ state is a prerequisite for its nuclear localization and chromosomal assembly. Likewise, we find that the closure motif is also necessary for the removal of ASY1 by PCH2 later in prophase. Our work results in a unified new model for PCH2 and HORMADs function in meiosis and suggests a mechanism to contribute to unidirectionality in meiosis.

TRIP13 promotes metastasis of colorectal cancer regardless of p53 and microsatellite instability status

Overexpression of TRIP13, a member of the AAA-ATPase family, is linked with various cancers, but its role in metastasis is unknown in colorectal cancer (CRC). In the current study, we investigated the role TRIP13 in experimental metastasis and its involvement in regulation of WNT/β-catenin and EGFR signaling pathways. Evaluation of formalin-fixed paraffin-embedded (FFPE) and frozen tissues of adenomas and CRCs, along with their corresponding normal samples, showed that TRIP13 was gradually increased in its phenotypic expression from adenoma to carcinoma and that its overexpression in CRCs was independent of patient's gender, age, race/ethnicity, pathologic stage, and p53 and microsatellite instability (MSI) status. Moreover, liver metastases of CRCs showed TRIP13 overexpression as compared to matched adjacent liver tissues, indicating the biological relevance of TRIP13 in CRC progression and metastasis. TRIP13 knockdown impeded colony formation, invasion, motility, and spheroid-forming capacity of CRC cells irrespective of their p53 and MSI status. Furthermore, xenograft studies demonstrated high expression of TRIP13 contributed to tumor growth and metastasis. Depletion of TRIP13 in CRC cells decreased metastasis and it was independent of the p53 and MSI status. Furthermore, TRIP13 interacted with a tyrosine kinase, FGFR4; this interaction could be essential for activation of the EGFR-AKT pathway. In addition, we demonstrated the involvement of TRIP13 in the Wnt signaling pathway and in the epithelial-mesenchymal transition. Cell-based assays revealed that miR-192 and PNPT1 regulate TRIP13 expression in CRC. Additionally, RNA sequencing of CRC cells with TRIP13 knockdown identified COL6A3, TREM2, SHC3, and KLK7 as downstream targets that may have functional relevance in TRIP13-mediated tumor growth and metastasis. In summary, our results demonstrated that TRIP13 promotes tumor growth and metastasis regardless of p53 and MSI status, and indicated that it is a target for therapy of CRC.

SAC during early cell divisions: Sacrificing fidelity over timely division, regulated differently across organisms: Chromosome alignment and segregation are left unsupervised from the onset of development until checkpoint activity is acquired, varying from species to species

Early embryogenesis is marked by a frail Spindle Assembly Checkpoint (SAC). The time of SAC acquisition varies depending on the species, cell size or a yet to be uncovered developmental timer. This means that for a specific number of divisions, biorientation of sister chromatids occurs unsupervised. When error-prone segregation is an issue, an aneuploidy-selective apoptosis system can come into play to eliminate chromosomally unbalanced cells resulting in healthy newborns. However, aneuploidy content can be too great to overcome, endangering viability. SAC generates a diffusible signal to lengthen time spent in mitosis if needed, ensuring correct chromosome segregation, a fundamental factor in the generation of euploid cells. Thus, it remains puzzling what benefit could come from delaying SAC acquisition till later in the development. In this review, we describe what is known on SAC acquisition in distinct species and highlight pending research as well as potential applications for such knowledge.

The conserved AAA-ATPase PCH-2 TRIP13 regulates spindle checkpoint strength

Spindle checkpoint strength is dictated by the number of unattached kinetochores, cell volume, and cell fate. We show that the conserved AAA-ATPase PCH-2/TRIP13, which remodels the checkpoint effector Mad2 from an active conformation to an inactive one, controls checkpoint strength in Caenorhabditis elegans. Having previously established that this function is required for spindle checkpoint activation, we demonstrate that in cells genetically manipulated to decrease in cell volume, PCH-2 is no longer required for the spindle checkpoint or recruitment of Mad2 at unattached kinetochores. This role is not limited to large cells: the stronger checkpoint in germline precursor cells also depends on PCH-2. PCH-2 is enriched in germline precursor cells, and this enrichment relies on conserved factors that induce asymmetry in the early embryo. Finally, the stronger checkpoint in germline precursor cells is regulated by CMT-1, the ortholog of p31^comet, which is required for both PCH-2′s localization to unattached kinetochores and its enrichment in germline precursor cells. Thus, PCH-2, likely by regulating the availability of inactive Mad2 at and near unattached kinetochores, governs checkpoint strength. This requirement may be particularly relevant in oocytes and early embryos enlarged for developmental competence, cells that divide in syncytial tissues, and immortal germline cells.

Homeostatic Control of Meiotic Prophase Checkpoint Function by Pch2 and Hop1

Checkpoint cascades link cell cycle progression with essential chromosomal processes. During meiotic prophase, recombination and chromosome synapsis are monitored by what are considered distinct checkpoints. In budding yeast, cells that lack the AAA+ ATPase Pch2 show an impaired cell cycle arrest in response to synapsis defects. However, unperturbed pch2Δ cells are delayed in meiotic prophase, suggesting paradoxical roles for Pch2 in cell cycle progression. Here, we provide insight into the checkpoint roles of Pch2 and its connection to Hop1, a HORMA domain-containing client protein. Contrary to current understanding, we find that Pch2 (together with Hop1) is crucial for checkpoint function in response to both recombination and synapsis defects, thus revealing a shared meiotic checkpoint cascade. Meiotic checkpoint responses are transduced by DNA break-dependent phosphorylation of Hop1. Based on our data and on the described effect of Pch2 on HORMA topology, we propose that Pch2 promotes checkpoint proficiency by catalyzing the availability of signaling-competent Hop1. Conversely, we demonstrate that Pch2 can act as a checkpoint silencer, also in the face of persistent DNA repair defects. We establish a framework in which Pch2 and Hop1 form a homeostatic module that governs general meiotic checkpoint function. We show that this module can-depending on the cellular context-fuel or extinguish meiotic checkpoint function, which explains the contradictory roles of Pch2 in cell cycle control. Within the meiotic prophase checkpoint, the Pch2-Hop1 module thus operates analogous to the Pch2/TRIP13-Mad2 module in the spindle assembly checkpoint that monitors chromosome segregation.

Thyroid receptor-interacting protein 13 and EGFR form a feedforward loop promoting glioblastoma growth

Epidermal growth factor receptor (EGFR) amplification and EGFRvIII mutation drive glioblastoma (GBM) pathogenesis, but their regulation remains elusive. Here we characterized the EGFR/EGFRvIII "interactome" in GBM and identified thyroid receptor-interacting protein 13 (TRIP13), an AAA + ATPase, as an EGFR/EGFRvIII-associated protein independent of its ATPase activity. Functionally, TRIP13 augmented EGFR pathway activation and contributed to EGFR/EGFRvIII-driven GBM growth in GBM spheroids and orthotopic GBM xenograft models. Mechanistically, TRIP13 enhanced EGFR protein abundance in part by preventing Cbl-mediated ubiquitination and proteasomal degradation. Reciprocally, TRIP13 was phosphorylated at tyrosine(Y) 56 by EGFRvIII and EGF-activated EGFR. Abrogating TRIP13 Y56 phosphorylation dramatically attenuated TRIP13 expression-enhanced EGFR signaling and GBM cell growth. Clinically, TRIP13 expression was upregulated in GBM specimens and associated with poor patient outcome. In GBM, TRIP13 localized to cell membrane and cytoplasma and exhibited oncogenic effects in vitro and in vivo, depending on EGFR signaling but not the TRIP13 ATPase activity. Collectively, our findings uncover that TRIP13 and EGFR form a feedforward loop to potentiate EGFR signaling in GBM growth and identify a previously unrecognized ATPase activity-independent mode of action of TRIP13 in GBM biology.

The role of Anaphase Promoting Complex activation, inhibition and substrates in cancer development and progression

The Anaphase Promoting Complex (APC), a multi-subunit ubiquitin ligase, facilitates mitotic and G1 progression, and is now recognized to play a role in maintaining genomic stability. Many APC substrates have been observed overexpressed in multiple cancer types, such as CDC20, the Aurora A and B kinases, and Forkhead box M1 (FOXM1), suggesting APC activity is important for cell health. We performed BioGRID analyses of the APC coactivators CDC20 and CDH1, which revealed that at least 69 proteins serve as APC substrates, with 60 of them identified as playing a role in tumor promotion and 9 involved in tumor suppression. While these substrates and their association with malignancies have been studied in isolation, the possibility exists that generalized APC dysfunction could result in the inappropriate stabilization of multiple APC targets, thereby changing tumor behavior and treatment responsiveness. It is also possible that the APC itself plays a crucial role in tumorigenesis through its regulation of mitotic progression. In this review the connections between APC activity and dysregulation will be discussed with regards to cell cycle dysfunction and chromosome instability in cancer, along with the individual roles that the accumulation of various APC substrates may play in cancer progression.

Identification of DGUOK-AS1 as a Prognostic Factor in Breast Cancer by Bioinformatics Analysis

Background: Significant developments have been made in breast cancer diagnosis and treatment, yet the prognosis remains unsatisfactory. Accumulating evidence indicates that long non-coding RNAs (lncRNAs) play pivotal roles in the development and progression of human tumors. However, the regulatory mechanisms and clinical significance of most lncRNAs in breast cancer remain poorly understood.

Methods: The lncRNA, miRNA, and mRNA expression profiles were obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. A lncRNA-miRNA-mRNA regulatory network was constructed and visualized using Cytoscape. The protein-protein interaction (PPI) network was constructed using the STRING database and hub genes were extracted using the cytoHubba plugin. Gene Ontology and Kyoto Encyclopedia of Gene and Genomes analyses identified the functions and signaling pathways associated with these differentially expressed mRNAs (DEmRNAs). Expression of the key lncRNA and the relationship with prognosis of patients with breast cancer were evaluated.

Results: Six differentially expressed lncRNAs (DElncRNAs), 29 differentially expressed miRNAs (DEmiRNAs), and 253 DEmRNAs were selected to construct the regulatory network. A PPI network was established and seven hub genes were identified. A lncRNA-miRNA-hub gene regulatory sub-network was established containing two DElncRNAs, five DEmiRNAs, and seven DEmRNAs. Hub genes were associated with breast cancer onset and progression. The upregulated DGUOK-AS1 was identified as the key lncRNA in breast cancer based on the competing endogenous RNA network. High DGUOK-AS1 expression was associated with adverse prognosis in patients with breast cancer and a prognostic nomogram built on Grade, LN status, and DGUOK-AS1 expression shows significant prognostic value.

Conclusions: Our results reveal the significant roles of lncRNA/miRNA/mRNA regulatory networks in breast cancer and identified a novel prognosis predictor and promising therapeutic target for patients with breast cancer.

Bi-allelic Missense Pathogenic Variants in TRIP13 Cause Female Infertility Characterized by Oocyte Maturation Arrest

Normal oocyte meiosis is a prerequisite for successful human reproduction, and abnormalities in the process will result in infertility. In 2016, we identified mutations in TUBB8 as responsible for human oocyte meiotic arrest. However, the underlying genetic factors for most affected individuals remain unknown. TRIP13, encoding an AAA-ATPase, is a key component of the spindle assembly checkpoint, and recurrent homozygous nonsense variants and a splicing variant in TRIP13 are reported to cause Wilms tumors in children. In this study, we identified homozygous and compound heterozygous missense pathogenic variants in TRIP13 responsible for female infertility mainly characterized by oocyte meiotic arrest in five individuals from four independent families. Individuals from three families suffered from oocyte maturation arrest, whereas the individual from the fourth family had abnormal zygote cleavage. All displayed only the infertility phenotype without Wilms tumors or any other abnormalities. In vitro and in vivo studies showed that the identified variants reduced the protein abundance of TRIP13 and caused its downstream molecule, HORMAD2, to accumulate in HeLa cells and in proband-derived lymphoblastoid cells. The chromosome mis-segregation assay showed that variants did not have any effects on mitosis. Injecting TRIP13 cRNA into oocytes from one affected individual was able to rescue the phenotype, which has implications for future therapeutic treatments. This study reports pathogenic variants in TRIP13 responsible for oocyte meiotic arrest, and it highlights the pivotal but different roles of TRIP13 in meiosis and mitosis. These findings also indicate that different dosage effects of mutant TRIP13 might result in two distinct human diseases.

Disassembly of the Shieldin Complex by TRIP13

In the past decade, the study of the major DNA double strand break (DSB) repair pathways, homologous recombination (HR) and classical non-homologous end joining (C-NHEJ), has revealed a vast and intricate network of regulation.  The choice between HR and C-NHEJ is largely controlled at the step of DNA end-resection. A pro-C-NHEJ cascade commencing with 53BP1 and culminating in the newly discovered REV7-Shieldin complex impedes end resection and therefore HR. Importantly, loss of any component of this pathway confers PARP inhibitor resistance in BRCA1-deficient cells; hence, their study is of great clinical importance. The newest entrant on the scene of end resection regulation is the ATPase TRIP13 that disables the pro-C-NHEJ cascade by promoting a novel conformational change of the HORMA protein REV7. Here, we tie these new findings and factors with previous research on the regulation of DSB repair and HORMA proteins, and suggest testable hypotheses for how TRIP13 could specifically inactivate REV7-Shieldin to promote HR. We also discuss these biological questions in the context of clinical therapeutics.

Interactions between N-terminal Modules in MPS1 Enable Spindle Checkpoint Silencing

Faithful chromosome segregation relies on the ability of the spindle assembly checkpoint (SAC) to delay anaphase onset until chromosomes are attached to the mitotic spindle via their kinetochores. MPS1 kinase is recruited to kinetochores to initiate SAC signaling and is removed from kinetochores once stable microtubule attachments have been formed to allow normal mitotic progression. Here, we show that a helical fragment within the kinetochore-targeting N-terminal extension (NTE) module of MPS1 is required for interactions with kinetochores and forms intramolecular interactions with its adjacent tetratricopeptide repeat (TPR) domain. Bypassing this NTE-TPR interaction results in high MPS1 levels at kinetochores due to loss of regulatory input into MPS1 localization, inefficient MPS1 delocalization upon microtubule attachment, and SAC silencing defects. These results show that SAC responsiveness to attachments relies on regulated intramolecular interactions in MPS1 and highlight the sensitivity of mitosis to perturbations in the dynamics of the MPS1-NDC80-C interactions.

Absence of the TRIP13 c.1060C>T Mutation in Wilms Tumor Patients From Pakistan

BACKGROUND AND AIM

Wilms tumor (WT) is the most common childhood malignant renal tumor. Germline mutations in several WT predisposition genes have been identified. However, the fundamental cause of most WT patients remains unexplained. Recently, a founder mutation, c.1060C>T (p. Arg254X) in a mitotic spindle checkpoint gene, TRIP13, was reported in 5 unrelated children with WT from the United Kingdom, of Pakistani descent from Azad Kashmir region. This observation suggests other children with WT in Pakistan may also harbor this mutation. We conducted the first study to assess the contribution of TRIP13 c.1060C>T mutation to WT in Pakistan.

MATERIALS AND METHODS

Constitutional genomic DNA from 68 Pakistani individuals including unrelated WT cases (n=26) and one (n=10) or both (n=32) of their parent(s) were screened for the TRIP13 c.1060C>T mutation using DNA sequence analysis. We also included positive controls in the analyses.

RESULTS

The median age of WT diagnosis was 3.0 years (range, 0.75 to 10). The TRIP13 c.1060C>T mutation was not found in any WT patient (n=26) or their parents (n=42). Twenty-four patients (92.4%) presented with unilateral tumor and 2 patients (7.7%) were diagnosed with synchronous bilateral WT. Thirteen patients (50%) reported parental consanguinity. Thirteen patients (50.0%) belonged to the Punjabi ethnicity and 1 patient (3.8%) had a Kashmiri background. Four patients (16.7%) reported a family history of WT or other malignancies. The predominant histologic subtype was stromal (46.2%). The majority of patients presented with >5 cm of tumor size (81%). None of the patients had a personal or family history of congenital anomalies, or associated genetic syndromes.

CONCLUSIONS

Our findings suggest that TRIP13 c.1060C>T mutation may be infrequent in Pakistani WT cases. Further evaluation of this mutation in a large number of WT patients of Kashmiri heritage and various ethnic backgrounds from Pakistan is warranted.

Mitotic slippage is determined by p31comet and the weakening of the spindle-assembly checkpoint

Mitotic slippage involves cells exiting mitosis without proper chromosome segregation. Although degradation of cyclin B1 during prolonged mitotic arrest is believed to trigger mitotic slippage, its upstream regulation remains obscure. Whether mitotic slippage is caused by APC/C^CDC20 activity that is able to escape spindle-assembly checkpoint (SAC)-mediated inhibition, or is actively promoted by a change in SAC activity remains an outstanding issue. We found that a major culprit for mitotic slippage involves reduction of MAD2 at the kinetochores, resulting in a progressive weakening of SAC during mitotic arrest. A further level of control of the timing of mitotic slippage is through p31^comet-mediated suppression of MAD2 activation. The loss of kinetochore MAD2 was dependent on APC/C^CDC20, indicating a feedback control of APC/C to SAC during prolonged mitotic arrest. The gradual weakening of SAC during mitotic arrest enables APC/C^CDC20 to degrade cyclin B1, cumulating in the cell exiting mitosis by mitotic slippage.

TRIP13 regulates DNA repair pathway choice through REV7 conformational change

DNA double-strand breaks (DSBs) are repaired through homology-directed repair (HDR) or non-homologous end joining (NHEJ). BRCA1/2-deficient cancer cells cannot perform HDR, conferring sensitivity to poly(ADP-ribose) polymerase inhibitors (PARPi). However, concomitant loss of the pro-NHEJ factors 53BP1, RIF1, REV7-Shieldin (SHLD1-3) or CST-DNA polymerase alpha (Pol-α) in BRCA1-deficient cells restores HDR and PARPi resistance. Here, we identify the TRIP13 ATPase as a negative regulator of REV7. We show that REV7 exists in active 'closed' and inactive 'open' conformations, and TRIP13 catalyses the inactivating conformational change, thereby dissociating REV7-Shieldin to promote HDR. TRIP13 similarly disassembles the REV7-REV3 translesion synthesis (TLS) complex, a component of the Fanconi anaemia pathway, inhibiting error-prone replicative lesion bypass and interstrand crosslink repair. Importantly, TRIP13 overexpression is common in BRCA1-deficient cancers, confers PARPi resistance and correlates with poor prognosis. Thus, TRIP13 emerges as an important regulator of DNA repair pathway choice-promoting HDR, while suppressing NHEJ and TLS.

TRIP13 promotes the cell proliferation, migration and invasion of glioblastoma through the FBXW7/c-MYC axis

Background

Thyroid hormone receptor interactor 13 (TRIP13) is an AAA + ATPase that plays an important role in the mitotic checkpoint. TRIP13 is highly expressed in various human tumours and promotes tumorigenesis. However, the biological effect of TRIP13 in GBM cells remains unclear.

Methods

We generated GBM cell models with overexpressed or silenced TRIP13 via lentivirus-mediated overexpression and RNAi methods. The biological role of TRIP13 in the proliferation, migration and invasion of GBM cells has been further explored.

Results

Our research indicated that TRIP13 was highly expressed in GBM tissues and cells. We found that the proliferation, migration and invasion abilities were inhibited in TRIP13-knockdown GBM cells. These results indicated that TRIP13 plays an important role in the tumorigenesis of GBM. Moreover, we found that TRIP13 first stabilised c-MYC by inhibiting the transcription of FBXW7, which is an E3 ubiquitin ligase of c-MYC, by directly binding to the promoter region of FBXW7. Therefore, our study indicated that the TRIP13/FBXW7/c-MYC pathway might provide a prospective therapeutic target in the treatment of GBM.

Conclusions

These results indicated that TRIP13 plays an oncogenic role in GBM. The TRIP13/FBXW7/c-MYC pathway might act as a prospective therapeutic target for GBM patients.

The oncogenic role of TRIP13 in regulating proliferation, invasion, and cell cycle checkpoint in NSCLC cells

TRIP13 (thyroid hormone receptor interacting protein 13) AAA-ATPase has been reported to be involved in the metaphase checkpoint in human breast cancer, prostate cancer, and cervical cancer. However, the expression pattern and biologic role of TRIP13 in non-small cell lung cancer (NSCLC) remained unknown. In our present study, real-time PCR and western blot were used to detect the expression level of TRIP13 in NSCLC tissues and cell lines. We found that the expression levels of TRIP13 mRNA and protein were significantly upregulated in cell lines and lung tissues. Knockdown of TRIP13 by lentivirus inhibited cell proliferation and invasion in both A549 and H1299 cells. Furthermore, flow cytometry, western blot and immunoprecipitation showed that the MCC complex was disassembled and cells became arrested in metaphase, when TRIP13 was inhibited. In conclusion, here we first report that TRIP13 acts as a tumor promoter in regulating cell proliferation, invasion, and cell cycle checkpoint in NSCLC cells and may be a clinically useful marker for the diagnosis and treatment of lung cancer.

The PSMA8 subunit of the spermatoproteasome is essential for proper meiotic exit and mouse fertility

The ubiquitin proteasome system regulates meiotic recombination in yeast through its association with the synaptonemal complex, a ‘zipper’-like structure that holds homologous chromosome pairs in synapsis during meiotic prophase I. In mammals, the proteasome activator subunit PA200 targets acetylated histones for degradation during somatic DNA double strand break repair and during histone replacement during spermiogenesis. We investigated the role of the testis-specific proteasomal subunit α4s (PSMA8) during spermatogenesis, and found that PSMA8 was localized to and dependent on the central region of the synaptonemal complex. Accordingly, synapsis-deficient mice show delocalization of PSMA8. Moreover, though Psma8-deficient mice are proficient in meiotic homologous recombination, there are alterations in the proteostasis of several key meiotic players that, in addition to the known substrate acetylated histones, have been shown by a proteomic approach to interact with PSMA8, such as SYCP3, SYCP1, CDK1 and TRIP13. These alterations lead to an accumulation of spermatocytes in metaphase I and II which either enter massively into apoptosis or give rise to a low number of aberrant round spermatids that apoptose before histone replacement takes place.

Proteins within the cells that are unnecessary or damaged are degraded by a large protein complex named the proteasome. The proteins to be degraded are marked by a small protein called ubiquitin. The addition of a small modification (acetyl group) to some proteins also promotes their degradation by the proteasome. Proteasomal degradation of proteins is an essential mechanism for many developmental programs including gametogenesis, a process whereby a diploid cell produces a haploid cell or gamete (sperm or egg). The mechanism by which this genome reduction occurs is called meiosis. Here, we report the study of a protein, named PSMA8 that is specific for the testis proteasome in vertebrates. Using the mouse as a model, we show that loss of PSMA8 leads to infertility in males. By co-immunoprecipitation-coupled mass spectroscopy we identified a large list of novel PSMA8 interacting proteins. We focused our functional analysis on several key meiotic proteins which were accumulated such as SYCP3, SYCP1, CDK1 and TRIP13 in addition to the known substrate of the spermatoproteasome, the acetylated histones. We suggest that the altered accumulation of these important proteins causes a disequilibrium of the meiotic division that produces apoptotic spermatocytes in metaphase I and II and also early spermatids that die soon after reaching this stage.