Inhibition of the ATG4-LC3 pathway suppressed osteoclast maturation.

Autophagy is a non-selective action in which cells degrade parts of themselves, reusing degraded cellular components. Among autophagy-related gene (ATG) family members, ATG4 proteins play crucial roles in the microtubule-associated protein 1 light chain 3 (LC3) phosphatidylethanolamine (PE) system which is essential for autophagosome maturation. Although autophagy has been shown to be involved in osteoclastic bone resorption, the role of ATG4/LC3 in bone resorption remains unclear. When mouse bone marrow cells were treated with various concentrations of NSC185058 (NSC), a specific inhibitor of ATG4B, 1 h prior to treatment with receptor activator of NF-κB ligand (RANKL) in the presence of macrophage colony stimulating factor (M-CSF), NSC inhibited osteoclastogenesis in a dose-dependent manner. Addition of NSC in the late stages of osteoclast differentiation suppressed multinucleation and reduced the expression of markers for mature osteoclasts such as Dc-stamp, Mmp9, and Ctsk. NSC also suppressed actin ring formation and pit formation in mature osteoclasts. When a periodontitis model involving eight-week-old male mice in which the right maxillary second molar had been ligated with silk thread was injected with or without NSC, alveolar bone resorption was suppressed by a decrease in the number of osteoclasts in the NSC-treated group. These results suggest that LC3 is important for the maturation of osteoclasts and that LC3 inhibition is a new therapeutic strategy for periodontal disease.

Development of a degrader against oncogenic fusion protein FGFR3-TACC3.

Fibroblast growth factor receptor 3-transforming acidic coiled-coil containing protein 3 (FGFR3-TACC3), which has been identified in many cancers such as glioblastoma and bladder cancer, is a potent oncogenic fusion protein that induces constitutive activation of FGFR signaling, resulting in uncontrolled cell proliferation. Although several tyrosine kinase inhibitors against FGFR are currently under development, resistance to such types of inhibitors in patients has become a concern. In this study, a chimeric molecule SNIPER(TACC3)-11 (5a) was developed and found to reduce FGFR3-TACC3 levels effectively. Compound 5a conjugated KHS108 (a TACC3 ligand) to an LCL161 derivative (11) (an inhibitor of apoptosis protein [IAP] ligand) with a PEG linker (n = 2). Mechanistical analysis showed that cellular IAP1 was required for the reduction of FGFR3-TACC3 levels. Consistent with the decrease in FGFR3-TACC3 levels, compound 5a suppressed the growth of FGFR3-TACC3 positive cells. Thus, compound 5a is a candidate therapeutic with a novel drug modality against cancers that exhibit FGFR3-TACC3-dependent proliferation and exerts pharmacological effects distinct from FGFR3 kinase inhibitors because it lacks substructures crucial for kinase inhibition.

The Arabidopsis AtGCD3 protein is a glucosylceramidase that preferentially hydrolyzes long-acyl-chain glucosylceramides.

Cellular membranes contain many lipids, some of which, such as sphingolipids, have important structural and signaling functions. The common sphingolipid glucosylceramide (GlcCer) is present in plants, fungi, and animals. As a major plant sphingolipid, GlcCer is involved in the formation of lipid microdomains, and the regulation of GlcCer is key for acclimation to stress. Although the GlcCer biosynthetic pathway has been elucidated, little is known about GlcCer catabolism, and a plant GlcCer-degrading enzyme (glucosylceramidase (GCD)) has yet to be identified. Here, we identified AtGCD3, one of four Arabidopsis thaliana homologs of human nonlysosomal glucosylceramidase, as a plant GCD. We found that recombinant AtGCD3 has a low Km for the fluorescent lipid C6-NBD GlcCer and preferentially hydrolyzes long acyl-chain GlcCer purified from Arabidopsis leaves. Testing of inhibitors of mammalian glucosylceramidases revealed that a specific inhibitor of human ß-glucosidase 2, N-butyldeoxynojirimycin, inhibits AtGCD3 more effectively than does a specific inhibitor of human ß-glucosidase 1, conduritol ß-epoxide. We also found that Glu-499 and Asp-647 in AtGCD3 are vital for GCD activity. GFP-AtGCD3 fusion proteins mainly localized to the plasma membrane or the endoplasmic reticulum membrane. No obvious growth defects or changes in sphingolipid contents were observed in gcd3 mutants. Our results indicate that AtGCD3 is a plant glucosylceramidase that participates in GlcCer catabolism by preferentially hydrolyzing long-acyl-chain GlcCers.

hsa-miR-7-5p suppresses proliferation, migration and promotes apoptosis in hepatocellular carcinoma cell lines by inhibiting SPC24 expression.

Emerging evidence suggests that microRNAs (miRNAs) participate in hepatocellular carcinoma (HCC) progression. Nevertheless, the mechanism of miR-7-5p in HCC cells has not been researched. In the research, the underlying biological function of miR-7-5p and SPC24 in HCC was explored. qRT-PCR was performed to measure the miR-7-5p and SPC24 level in HCC tissues and cells. The effect of miR-7-5p on HCC progression was detected by performing CCK-8, BrdU, and transwell assay. The relationship between miR-7-5p and SPC24 was determined using luciferase and RNA pull-down assays. Our findings showed that miR-7-5p was downregulated in HCC whereas SPC24 was upregulated in HCC. It was also showed that miR-7-5p upregulation restricted malignant behaviors of HCC cells, but this inhibitory effect of miR-7-5p could be relieved by its target gene SPC24. In conclusion, this research suggested that by inhibiting SPC24, miR-7-5p could act as a tumor inhibitory factor in HCC.

TPX2 mediates prostate cancer epithelial-mesenchymal transition through CDK1 regulated phosphorylation of ERK/GSK3ß/SNAIL pathway.

Prostate cancer with high Gleason grade is prone to metastasis, which is one of the factors that seriously threaten the survival of patients, and it is also a treatment difficulty. In this study, we first revealed the potential connection between TPX2 and prostate cancer metastasis. We found that TPX2 is highly expressed in high-grade prostate cancer and is significantly related to poor prognosis. Depletion of TPX2 can significantly inhibit cell activity and migration, and in vivo experiments show that knockdown of TPX2 can significantly inhibit tumor growth. In terms of mechanism, we found that knocking down TPX2 can inhibit the expression of CDK1, repress the phosphorylation of ERK/GSK3ß/SNAIL signaling pathway, and thereby inhibit tumor epithelial-mesenchymal transition. Subsequently, we found that after rescuing TPX2, all related proteins and phenotype changes were restored, and this effect can be inhibited by CDK1 inhibitor, RO-3306. Our findings suggest the potential of TPX2 as an important target in anti-tumor metastasis therapy, which is conducive to precision medicine for prostate cancer.

Microtubule-associated protein 2 mediates induction of long-term potentiation in hippocampal neurons.

Microtubule-associated protein (MAP) 2 has been perceived as a static cytoskeletal protein enriched in neuronal dendritic shafts. Emerging evidence indicates dynamic functions for various MAPs in activity-dependent synaptic plasticity. However, it is unclear how MAP2 is associated with synaptic plasticity mechanisms. Here, we demonstrate that specific silencing of high-molecular-weight MAP2 in vivo abolished induction of long-term potentiation (LTP) in the Schaffer collateral pathway of CA1 pyramidal neurons and in vitro blocked LTP-induced surface delivery of AMPA receptors and spine enlargement. In mature hippocampal neurons, we observed rapid translocation of a subpopulation of MAP2, present in dendritic shafts, to spines following LTP stimulation. Time-lapse confocal imaging showed that spine translocation of MAP2 was coupled with LTP-induced spine enlargement. Consistently, immunogold electron microscopy revealed that LTP stimulation of the Schaffer collateral pathway promoted MAP2 labeling in spine heads of CA1 neurons. This translocation depended on NMDA receptor activation and Ras-MAPK signaling. Furthermore, LTP stimulation led to an increase in surface-expressed AMPA receptors specifically in the neurons with MAP2 spine translocation. Altogether, this study indicates a novel role for MAP2 in LTP mechanisms and suggests that MAP2 participates in activity-dependent synaptic plasticity in mature hippocampal networks.

TBK-1 promotes autophagy-mediated antimicrobial defense by controlling autophagosome maturation.

Autophagy is a fundamental biological process of the eukaryotic cell contributing to diverse cellular and physiological functions including cell-autonomous defense against intracellular pathogens. Here, we screened the Rab family of membrane trafficking regulators for effects on autophagic elimination of Mycobacterium tuberculosis var. bovis BCG and found that Rab8b and its downstream interacting partner, innate immunity regulator TBK-1, are required for autophagic elimination of mycobacteria in macrophages. TBK-1 was necessary for autophagic maturation. TBK-1 coordinated assembly and function of the autophagic machinery and phosphorylated the autophagic adaptor p62 (sequestosome 1) on Ser-403, a residue essential for its role in autophagic clearance. A key proinflammatory cytokine, IL-1ß, induced autophagy leading to autophagic killing of mycobacteria in macrophages, and this IL-1ß activity was dependent on TBK-1. Thus, TBK-1 is a key regulator of immunological autophagy and is responsible for the maturation of autophagosomes into lytic bactericidal organelles.

Computational design of binder as the LC3-p62 protein-protein interaction.

Cellular autophagy is an intracellular degradation pathway, which transports damaged, deformed, senescent or non-functional proteins and organelles to lysosome for digestion and degradation. Cellular autophagy is deeply evolutionarily conservedfromyeasttomammaliancells, and many homologous proteins of the autophahgy regulators are found in several species. This physiological process maintains the steady state of cells. Furtheremore, autophagy dysfunction is closely related to various diseases, such as neurodegenerative diseases, inflammation-related diseases, cardiovascular diseases, metabolic diseases, etc. The LC3 and p62 protein protein interaction (PPI) promotes the formation of autophagosomes and delivers polyubiquitinated "cargoes" to autophagic degradation. Therefore, LC3-p62 PPI plays an integral role in the formation of autophagosomes and effectively inhibits autophagy. However, there are still few studies on the LC3-p62 PPI inhibitors for its unclear molecular mechanism. Furthermore, most of these inhibitors are macromolecules with poorly active, and small molecules are particularly scarce. In this article, the computation method was used to identify the hot spot and design peptides as the binder of LC3-p62 PPI. Findings from this work provide a reference for the follow-up research of discovering small molecule inhibitors targeting LC3-p62 PPI.

Microtubule associated proteins as targets for anticancer drug development.

The dynamic equilibrium of tubulin-microtubule is an essential aspect of cell survivality. Modulation of this dynamics has become an important target for the cancer drug development. Tubulin exists in the alpha-beta dimer form which polymerizes to form microtubule and further depolymerizes back to tubulin dimer. The microtubule plays an essential role in mitosis and cell multiplication. Antitubulin drugs disturb the microtubule dynamics which is essentially required for DNA segregation and cell division during mitosis so killing the cancerous cells. Microtubule Associated Proteins (MAPs) interact with cellular cytoskeletal microtubules. MAPs bind to the either polymerized or depolymerized tubulin dimers within the cell and mostly causing stabilization of microtubules. Some of the tubulin binding drugs are in clinical use and others in clinical trial. MAPs inhibitors are also in clinical trial. Post-translational modification of lysine-40 either in histone or in alpha tubulin has an important role in gene expression and is balanced between histone deacetylases (HDACs) and histone acetyltransferases (HATs). HDAC inhibitors have the anticancer properties to form a drug for the treatment of cancer. They act by inducing cell cycle arrest and cell death. Some of the HDAC inhibitors are approved to be used as anticancer drug while others are under different phases of clinical trial. The present review updates on various MAPs, their role in cancer progression, MAPs inhibitors and their future prospects.

TACC3 promotes prostate cancer cell proliferation and restrains primary cilium formation.

Although primary cilia abnormalities have been frequently observed in multiple cancers, including prostate cancer (PCa), the molecular mechanisms underlying primary ciliogenesis repression in PCa cells remain unclear. Transforming acidic coiled-coil protein-3 (TACC3), whose deregulation has been implicated in the pathogenesis of several types of cancer, is a key centrosomal protein that plays a crucial role in centrosome/microtubule dynamics, potentially impacting primary cilium generation. Here, we showed that TACC3 was markedly upregulated in PCa and that knockdown of TACC3 restrained tumorigenesis and tumor growth in vitro and in vivo. Additionally, we found that TACC3 interacts with filamin A, and elevated levels of TACC3 disrupted the interaction between filamin A and meckelin, thereby restraining primary cilium formation in PCa cells.

Antagonism between BRCA2 and FIGL1 regulates homologous recombination.

Homologous recombination (HR) maintains genome stability by promoting accurate DNA repair. Two recombinases, RAD51 and DMC1, are central to HR repair and form dynamic nucleoprotein filaments in vivo under tight regulation. However, the interplay between positive and negative regulators to control the dynamic assembly/disassembly of RAD51/DMC1 filaments in multicellular eukaryotes remains poorly characterized. Here, we report an antagonism between BRCA2, a well-studied positive mediator of RAD51/DMC1, and FIDGETIN-LIKE-1 (FIGL1), which we previously proposed as a negative regulator of RAD51/DMC1. Through forward genetic screen, we identified a mutation in one of the two Arabidopsis BRCA2 paralogs that suppresses the meiotic phenotypes of figl1. Consistent with the antagonistic roles of BRCA2 and FIGL1, the figl1 mutation in the brca2 background restores RAD51/DMC1 focus formation and homologous chromosome interaction at meiosis, and RAD51 focus formation in somatic cells. This study shows that BRCA2 and FIGL1 have antagonistic effects on the dynamics of RAD51/DMC1-dependent DNA transactions to promote accurate HR repair.

Acetyl-L-carnitine confers neuroprotection against lipopolysaccharide (LPS) -induced neuroinflammation by targeting TLR4/NFκB, autophagy, inflammation and oxidative stress.

Acetyl-L-carnitine has been shown to exert neuroprotection against neurodegenerative diseases. The present study was performed to evaluate neuroprotection effects of acetyl-L-carnitine against lipopolysaccharide (LPS) -induced neuroinflammation and clarify possible mechanisms. A single dose (500 µg/kg) of LPS was intraperitoneally injected to rats to induce model. The animals were intraperitoneally treated with different doses of acetyl-L-carnitine (30, 60, and 100) for 6 days. Y-maze task, single-trial passive avoidance and novel object recognition tests were used to evaluate memory impairments. ELISA assay was used to evaluate the expression of TLR4/NFκB, autophagic and oxidative stress markers. Our result showed that intraperitoneal injection of LPS resulted in initiation of neuroinflammation by activation of TLR4/NFκB, suppression of autophagic markers such as LC3 II/ LC3 I ratio and becline-1, and excessive production of ROS and MDA. Intraperitoneal administration of acetyl-L-carnitine contributed to neuroprotection against LPS -induced neuroinflammation by suppression of TLR4/NFκB pathway, restoring activity of autophagy and inhibition of oxidative stress. Collectively, our findings show that acetyl-L-carnitine attenuated LPS-induced neuroinflammation by targeting TLR4/NFκB pathway, autophagy and oxidative stress.

Structure-Based Design, Docking and Binding Free Energy Calculations of A366 Derivatives as Spindlin1 Inhibitors.

The chromatin reader protein Spindlin1 plays an important role in epigenetic regulation, through which it has been linked to several types of malignant tumors. In the current work, we report on the development of novel analogs of the previously published lead inhibitor A366. In an effort to improve the activity and explore the structure-activity relationship (SAR), a series of 21 derivatives was synthesized, tested in vitro, and investigated by means of molecular modeling tools. Docking studies and molecular dynamics (MD) simulations were performed to analyze and rationalize the structural differences responsible for the Spindlin1 activity. The analysis of MD simulations shed light on the important interactions. Our study highlighted the main structural features that are required for Spindlin1 inhibitory activity, which include a positively charged pyrrolidine moiety embedded into the aromatic cage connected via a propyloxy linker to the 2-aminoindole core. Of the latter, the amidine group anchor the compounds into the pocket through salt bridge interactions with Asp184. Different protocols were tested to identify a fast in silico method that could help to discriminate between active and inactive compounds within the A366 series. Rescoring the docking poses with MM-GBSA calculations was successful in this regard. Because A366 is known to be a G9a inhibitor, the most active developed Spindlin1 inhibitors were also tested over G9a and GLP to verify the selectivity profile of the A366 analogs. This resulted in the discovery of diverse selective compounds, among which 1s and 1t showed Spindlin1 activity in the nanomolar range and selectivity over G9a and GLP. Finally, future design hypotheses were suggested based on our findings.

MicroRNA-203-mediated inhibition of doublecortin underpins cardioprotection conferred by sevoflurane in rats after myocardial ischaemia-reperfusion injury.

Myocardial ischaemia-reperfusion (I/R) injury is a serious illness with high morbidity and mortality. Mounting evidence indicates the utility of sevoflurane (SEV) in the treatment of myocardial I/R injury. This study aimed to explore the molecular mechanisms underlying the protective action of SEV against myocardial I/R injury. A rat model of myocardial I/R injury was established, and I/R rats were treated with different concentrations of SEV. MicroRNA-203 (miR-203) and doublecortin (DCX) expression levels were determined using reverse transcription-quantitative polymerase chain reaction. Putative target relationship between miR-203 and DCX was explored using dual-luciferase reporter gene assay and RNA-binding protein immunoprecipitation assay. Ischaemia-reperfusion rats were treated with SEV, miR-203 antagomir or sh-DCX, followed by determination of oxidative stress- and inflammation-related factor levels using nitrite and enzyme-linked immunosorbent assays, and that of apoptosis-related factors using Western blot analysis. The apoptotic rate of myocardial tissues was determined using TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining, and the infract area was evaluated using triphenyltetrazolium chloride staining. The results showed miR-203 was poorly expressed and DCX was highly expressed in myocardial tissues of I/R rats. Sevoflurane was found to elevate miR-203, and miR-203, in turn, could target and reduce DCX expression. Sevoflurane, miR-203 overexpression or DCX silencing resulted in declined oxidative stress, inflammation, apoptosis and infarct area, ultimately alleviating myocardial I/R injury. Collectively, these findings showed that SEV-activated miR-203 exhibited suppressive effects on myocardial I/R injury in rats and highlighted the SEV/miR-203/DCX axis as a promising therapeutic target for myocardial I/R injury management.

NUSAP1 knockdown inhibits cell growth and metastasis of non-small-cell lung cancer through regulating BTG2/PI3K/Akt signaling.

Non-small-cell lung cancer (NSCLC) is the most common malignancy along with high mortality rate worldwide. Recently, nucleolar and spindle-associated protein 1 (NUSAP1) has been reported to be involved in the malignant progression of several cancers. However, in NSCLC, the biological function of NUSAP1 and its molecular mechanism have not been reported. Here, our findings indicated that the NUSAP1 messenger RNA expression level was remarkably upregulated in NSCLC tissues compared with that of adjacent normal tissues. We also found that NUSAP1 gene expression was notably upregulated in NSCLC cell lines (A549, 95-D, H358, and H1299) compared with that of normal human bronchial epithelial cell line (16HBE). Subsequently, the biological function of NUSAP1 was investigated in A549 and H358 cells transfected with NUSAP1 small interfering RNA (siRNA), respectively. Results showed that NUSAP1 knockdown inhibited NSCLC cell proliferation, and promoted cell apoptosis. Furthermore, the number of cell migration and invasion was significantly suppressed by NUSAP1 knockdown. In addition, our results indicated that NUSAP1 knockdown increased the gene expression of B-cell translocation gene 2 (BTG2), but decreased the expression levels of phosphoinositide 3-kinase (PI3K) and phosphorylated serine/threonine kinase (p-AKT). BTG2 siRNA partly abrogates the effect of NUSAP1 knockdown on BTG2 gene expression. Fumonisin B1 (FB1), a AKT activator, reversed the effect of NUSAP1 knockdown on the biological function in NSCLC. Taken together, NUSAP1 knockdown promotes NSCLC cell apoptosis, and inhibits cell proliferation, cell migration, and invasion, which is associated with regulating BTG2/PI3K/Akt signal pathway. Our findings suggest that NUSAP1 is a promising molecular target for NSCLC treatment.

The role of nucleolar spindle-associated protein 1 in human ovarian cancer.

Ovarian cancer (OC) is one of the deadliest malignancies of the female reproductive system. The present study focused on the role of Nucleolar spindle-associated protein 1 (NuSAP1) in OC. Relative expression of NuSAP1 was detected in OC tissues as well as cells. After knocking down NuSAP1 with lentivirus-mediated shRNA and verifying the knockdown efficiency via quantitative real-time polymerase chain reaction and Western blot assays, the cell proliferation, apoptosis, and cell cycle were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation, and flow cytometry, respectively. Transwell assay was conducted to detect the migration and invasion of OC cells. It was showed that NuSAP1 was abundantly expressed in OC tissues and cell lines. After knocking down NuSAP1 in OC cells, in addition to significantly inhibiting proliferation and colony forming ability, it also promotes apoptosis and affects cell cycle distribution. Moreover, cells in the shNuSAP1 group showed significantly suppressed migration and invasion ability compared with that in the shCtrl group. In conclusion, NuSAP1 may act as an oncogenic factor in OC and therefore might serve as an indicator for prognosis and therapeutic target for OC treatment.

Stapled Peptide Inhibitors of Autophagy Adapter LC3B.

A growing body of evidence suggests that autophagy inhibition enhances the effectiveness of chemotherapy, especially in difficult-to-treat cancers. Existing autophagy inhibitors are primarily lysosomotropic agents. More specific autophagy inhibitors are highly sought-after. The microtubule-associated protein 1A/1B light chain 3B protein, LC3B, is an adapter protein that mediates key protein-protein interactions at several points in autophagy pathways. In this work, we used a known peptide ligand as a starting point to develop improved LC3B inhibitors. We obtained structure-activity relationships that quantify the binding contributions of peptide termini, individual charged residues, and hydrophobic interactions. Based on these data, we used artificial amino acids and diversity-oriented stapling to improve affinity and resistance to biological degradation, while maintaining or improving LC3B affinity and selectivity. These peptides represent the highest-affinity LC3B-selective ligands reported to date, and they will be useful tools for further elucidation of LC3B's role in autophagy and in cancer.

Haemophilus parasuis infection in 3D4/21 cells induces autophagy through the AMPK pathway.

Haemophilus parasuis (H. parasuis) is a common commensal in the upper respiratory tract of pigs, but causes Glässer's disease in stress conditions. To date, many studies focused on the immune evasion and virulence of H. parasuis; very few have focused on the role autophagy played in H. parasuis infection, particularly in porcine alveolar macrophages (PAMs). In this study, a PAM cell line, 3D4/21 cells were used to study the role of autophagy in H. parasuis infection. 3D4/21 cells tandemly expressing GFP, mCherry, and LC3 were infected with H. parasuis serovar 5 (Hps5). Western blot analysis and confocal and transmission electron microscopy showed that H. parasuis infection effectively induces autophagy. Using Hps strains of varying virulence (Hps4, Hps5, and Hps7) and UV-inactivated Hps5, we demonstrated that autophagy is associated with the internalisation of living virulent strains into cells. In 3D4/21 cells pretreated with rapamycin and 3-MA then infected by Hps4, Hps5, and Hps7, we demonstrated that autophagy affects invasion of H. parasuis in cells. AMPK signal results showed that Hps5 infection can upregulate the phosphorylation level of AMPK, which is consistent with the autophagy development. 3D4/21 cells pretreated with AICAR or Compound C then infected by Hps5 revealed that the autophagy induced by Hps5 infection is associated with the AMPK pathway. Our study contributes to the theoretical basis for the study of H. parasuis pathogenesis and development of novel drugs target for prevention Glässer's disease.

Identification of phlebovirus and arenavirus RNA sequences that stall and repress the exoribonuclease XRN1.

Regulated mRNA decay plays a vital role in determining both the level and quality of cellular gene expression. Viral RNAs must successfully evade this host RNA decay machinery to establish a productive infection. One way for RNA viruses to accomplish this is to target the cellular exoribonuclease XRN1, because this enzyme is accessible in the cytoplasm and plays a major role in mRNA decay. Members of the Flaviviridae use RNA structures in their 5'- or 3'-untranslated regions to stall and repress XRN1, effectively stabilizing viral RNAs while also causing significant dysregulation of host cell mRNA stability. Here, we use a series of biochemical assays to demonstrate that the 3'-terminal portion of the nucleocapsid (N) mRNA of Rift Valley fever virus, a phlebovirus of the Bunyaviridae family, also can effectively stall and repress XRN1. The region responsible for impeding XRN1 includes a G-rich portion that likely forms a G-quadruplex structure. The 3'-terminal portions of ambisense-derived transcripts of multiple arenaviruses also stalled XRN1. Therefore, we conclude that RNAs from two additional families of mammalian RNA viruses stall and repress XRN1. This observation. emphasizes the importance and commonality of this viral strategy to interfere with the 5'-to-3'-exoribonuclease component of the cytoplasmic RNA decay machinery.

The microtubule-associated protein HURP recruits the centrosomal protein TACC3 to regulate K-fiber formation and support chromosome congression.

Kinetochore fibers (K-fibers) are microtubule bundles attached to chromosomes. Efficient K-fiber formation is required for chromosome congression, crucial for faithful chromosome segregation in cells. However, the mechanisms underlying K-fiber formation before chromosome biorientation remain unclear. Depletion of hepatoma up-regulated protein (HURP), a RanGTP-dependent microtubule-associated protein localized on K-fibers, has been shown to result in low-efficiency K-fiber formation. Therefore, here we sought to identify critical interaction partners of HURP that may modulate this function. Using co-immunoprecipitation and bimolecular fluorescence complementation assays, we determined that HURP interacts directly with the centrosomal protein transforming acidic coiled coil-containing protein 3 (TACC3), a centrosomal protein, both in vivo and in vitro through the HURP1-625 region. We found that HURP is important for TACC3 function during kinetochore microtubule assembly at the chromosome region in prometaphase. Moreover, HURP regulates stable lateral kinetochore attachment and chromosome congression in early mitosis by modulation of TACC3. These findings provide new insight into the coordinated regulation of K-fiber formation and chromosome congression in prometaphase by microtubule-associated proteins.