PSPC1 Binds to HCV IRES and Prevents Ribosomal Protein S5 Binding, Inhibiting Viral RNA Translation.

Hepatitis C virus (HCV) infects the human liver, and its chronic infection is one of the major causes of Hepatocellular carcinoma. Translation of HCV RNA is mediated by an Internal Ribosome Entry Site (IRES) element located in the 5'UTR of viral RNA. Several RNA Binding proteins of the host interact with the HCV IRES and modulate its function. Here, we demonstrate that PSPC1 (Paraspeckle Component 1), an essential paraspeckle component, upon HCV infection is relocalized and interacts with HCV IRES to prevent viral RNA translation. Competition UV-crosslinking experiments showed that PSPC1 interacts explicitly with the SLIV region of the HCV IRES, which is known to play a vital role in ribosomal loading to the HCV IRES via interaction with Ribosomal protein S5 (RPS5). Partial silencing of PSPC1 increased viral RNA translation and, consequently, HCV replication, suggesting a negative regulation by PSPC1. Interestingly, the silencing of PSPC1 protein leads to an increased interaction of RPS5 at the SLIV region, leading to an overall increase in the viral RNA in polysomes. Overall, our results showed how the host counters viral infection by relocalizing nuclear protein to the cytoplasm as a survival strategy.

Role of RNA binding proteins of the Drosophila behavior and human splicing (DBHS) family in health and cancer.

RNA-binding proteins (RBPs) play crucial roles in the functions and homoeostasis of various tissues by regulating multiple events of RNA processing including RNA splicing, intracellular RNA transport, and mRNA translation. The Drosophila behavior and human splicing (DBHS) family proteins including PSF/SFPQ, NONO, and PSPC1 are ubiquitously expressed RBPs that contribute to the physiology of several tissues. In mammals, DBHS proteins have been reported to contribute to neurological diseases and play crucial roles in cancers, such as prostate, breast, and liver cancers, by regulating cancer-specific gene expression. Notably, in recent years, multiple small molecules targeting DBHS family proteins have been developed for application as cancer therapeutics. This review provides a recent overview of the functions of DBHS family in physiology and pathophysiology, and discusses the application of DBHS family proteins as promising diagnostic and therapeutic targets for cancers.

SKP2 promotes the metastasis of pancreatic ductal adenocarcinoma by suppressing TRIM21-mediated PSPC1 degradation.

Despite significant advances in diagnostic techniques and treatment approaches, the prognosis of pancreatic ductal adenocarcinoma (PDAC) is still poor. Previous studies have reported that S-phase kinase-associated protein 2 (SKP2), a subunit of the SCF E3 ubiquitin ligase complex, is engaged in the malignant biological behavior of some tumor entities. However, SKP2 has not been fully investigated in PDAC. In the present study, it was observed that high expression of SKP2 significantly correlates with decreased survival time. Further experiments suggested that SKP2 promotes metastasis by interacting with the putative transcription factor paraspeckle component 1 (PSPC1). According to the results of coimmunoprecipitation and ubiquitination assays, SKP2 depletion resulted in the polyubiquitination of PSPC1, followed by its degradation. Furthermore, the SKP2-mediated ubiquitination of PSPC1 partially depended on the activity of the E3 ligase TRIM21. In addition, inhibition of the SKP2/PSPC1 axis by SMIP004, a traditional inhibitor of SKP2, impaired the migration of PDAC cells. In summary, this study provides novel insight into the mechanisms involved in PDAC malignant progression. Targeting the SKP2/PSPC1 axis is a promising strategy for the treatment of PDAC.

Design, development, and assessment of a novel multi-peptide vaccine targeting PspC, PsaA, and PhtD proteins of Streptococcus pneumoniae.

Pneumococcus is the top cause of diseases such as pneumonia/meningitis, and of secondary infections after viral respiratory diseases like COVID-19/flu. Pneumococcal protein-based vaccines consisting of proteins with various functions in virulence might provide a qualified alternative for present vaccines. In this project, PspC, PsaA, and PhtD proteins were considered to anticipate B/T-cell epitopes using immunoinformatics to develop 4 multi-peptide constructs (C, A, and D individual constructs, and a fusion construct CAD). We tested whether vaccination with CAD is able to elicit more efficient protective responses against infection than vaccination with the individual constructs or combination of C + A + D. Based on the in silico results, the constructs were predicted to be antigenic, soluble, non-toxic, and stable, and also be able to provoke humoral/cellular immune reactions. When mice were immunized with the fusion protein, significantly higher levels of IgG and cytokines were induced in serum. The IgG in the fusion group had an effective bioactivity for pneumococcus clearance utilizing the complement pathway. The mice immunized with fusion protein were the most protected from challenge. This report for the first time presents a novel multi-peptide vaccine composed of immunodominant peptides of PspC, PsaA, and PhtD. In general, the experimental results supported the immunoinformatics predictions.

PSPC1 Inhibition Synergizes with Poly(ADP-ribose) Polymerase Inhibitors in a Preclinical Model of BRCA-Mutated Breast/Ovarian Cancer.

Poly (ADP-ribose) polymerase (PARP) inhibitors are effective against BRCA1/2-mutated cancers through synthetic lethality. Unfortunately, most cases ultimately develop acquired resistance. Therefore, enhancing PARP inhibitor sensitivity and preventing resistance in those cells are an unmet clinical need. Here, we investigated the ability of paraspeckle component 1 (PSPC1), as an additional synthetic lethal partner with BRCA1/2, to enhance olaparib sensitivity in preclinical models of BRCA1/2-mutated breast and ovarian cancers. In vitro, the combined olaparib and PSPC1 small interfering RNA (siRNA) exhibited synergistic anti-proliferative activity in BRCA1/2-mutated breast and ovarian cancer cells. The combination therapy also demonstrated synergistic tumor inhibition in a xenograft mouse model. Mechanistically, olaparib monotherapy increased the expressions of p-ATM and DNA-PKcs, suggesting the activation of a DNA repair pathway, whereas combining PSPC1 siRNA with olaparib decreased the expressions of p-ATM and DNA-PKcs again. As such, the combination increased the formation of γH2AX foci, indicating stronger DNA double-strand breaks. Subsequently, these DNA-damaged cells escaped G2/M checkpoint activation, as indicated by the suppression of p-cdc25C (Ser216) and p-cdc2 (Tyr15) after combination treatment. Finally, these cells entered mitosis, which induced increased apoptosis. Thus, this proves that PSPC1 inhibition enhances olaparib sensitivity by targeting DNA damage response in our preclinical model. The combination of olaparib and PSPC1 inhibition merits further clinical investigation to enhance PARP inhibitor efficacy.

Negligible role for pneumococcal surface protein A (PspA) and pneumococcal surface protein C (PspC) in the nasopharyngeal colonization of mice with a serotype 6B pneumococcal strain.

Streptococcus pneumoniae colonizes the human nasopharynx asymptomatically, but it can also cause several diseases, including otitis media, pneumonia, bacteremia, and meningitis. The colonization of the nasopharynx by the bacteria is an essential step for the pneumococcus to invade other sites and cause diseases. Pneumococcal surface protein A (PspA) and Pneumococcal surface Protein C (PspC) are important virulence factors and have been described to play roles in adhesion and immune evasion. In this study, we immunized mice subcutaneously with the recombinant α-helical region of PspA and/or PspC combined with different adjuvants to assess protection against colonization with the serotype 6B strain BHN418. Though high serum levels of specific IgG were detected, none of the formulations led to reduction in the colonization of the nasopharynx. The negative result may be due to the poor induction of IgG2c, which has been previously correlated with protection against pneumococcal colonization in mice. Furthermore, BHN418 pspA and pspC single and double knockouts were evaluated in colonization experiments and no differences in bacterial load were observed. In competition assays with the wild-type strain, borderline to no reduction was observed in the loads of the knockouts. Our results contrast with data from the literature using other pneumococcal strains, showing that the role of PspA and PspC in colonization can vary depending on the background of the knockout strain studied. BHN418 has been selected for its capacity to colonize humans in experimental challenge studies and may have redundant factors that compensate for the lack of PspA and PspC during nasopharyngeal colonization of mice.

Meta-Structure Hull Design with Periodic Layered Phononic Crystals Theory for Wide-Band Low-Frequency Sound Insolation.

The hulls of marine vehicles are generally very effective at attenuating airborne acoustic noise generated by their powertrains. However, conventional hull designs are generally not very effective at attenuating wide-band low-frequency noise. Meta-structure concepts offer an opportunity for the design of laminated hull structures tailored to address this concern. This research proposes a novel meta-structure laminar hull concept using periodic layered Phononic crystals to optimize the sound insolation performance on the air-solid side of the hull structure. The acoustic transmission performance is evaluated using the transfer matrix, the acoustic transmittance, and the tunneling frequencies. The theoretical and numerical models for a proposed thin solid-air sandwiched meta-structure hull indicate ultra-low transmission within a 50-to-800 Hz frequency band and with two predicted sharp tunneling peaks. The corresponding 3D-printed sample experimentally validates the tunneling peaks at 189 Hz and 538 Hz, with 0.38 and 0.56 transmission magnitudes, respectively, with the frequency band between those values showing wide-band mitigation. The simplicity of this meta-structure design provides a convenient way to achieve acoustic band filtering of low frequencies for marine engineering equipment and, accordingly, an effective technique for low-frequency acoustic mitigation.

Elevated PSPC1 and KDM5C expression indicates poor prognosis in prostate cancer.

Prostate cancer (PCa) remains the most commonly diagnosed cancer in men worldwide and is still the second leading cause of cancer-related death. One major cause of PCa development is epigenetic aberration, including histone modification. We have previously demonstrated that Lysine Demethylase 5C (KDM5C) plays an essential role in the development of PCa and drives PCa progression by promoting epithelial-mesenchymal transition. Epigenetic regulators often work in concert, for example, to regulate transcription. We identified Paraspeckle Component 1 (PSPC1) as an interacting protein of KDM5C, suggesting that these proteins might function together in PCa. Here, we systematically investigate the expression patterns of KDM5C and PSPC1 in 2 independent prostate cohorts (432 and 205 prostate tumors in total for PSPC1 and KDM5C, respectively) by immunohistochemistry. We demonstrate that the expression of PSPC1 correlates with that of KDM5C. In addition, PSPC1 is up-regulated in primary and metastatic PCa. Elevated PSPC1 expression correlates with a higher-grade group and an advanced T-stage. Patients with high PSPC1 expression have a worse biochemical recurrence-free survival. In addition, PSPC1 expression is an independent prognostic parameter. Our data indicate that KDM5C and PSPC1 are involved in PCa progression, and therapeutic inhibition of KDM5C and PSPC1 by selective compounds might be a promising approach for the treatment of PCa.

STAT3 inhibitor BBI608 reduces patient-specific primary cell viability of cervical and endometrial cancer at a clinical-relevant concentration

Aberrant activation of STAT3 signal pathway promotes tumor progression in many solid tumor types, including cervical cancer and endometrial cancer. BBI608, the STAT3 inhibitor had been reported in previous studies for restraining cancer stem cells. However, whether BBI608 is available for inhibiting the proliferation of cervical cancer or endometrial cancer remains poorly understood. This study investigated the anti-tumor effect and molecular mechanism of BBI608 on the patient-specific primary cells (PSPC) generated from cervical and endometrial cancer in vitro. Methods PSPCs were obtained from four patients via biopsy. The cell viability was analyzed by the CCK8 assay. The PSPCs were treated with various concentrations of BBI608 or/and paclitaxel; and then, western blot was applied to investigate the expression of phosphorylated STAT3 (pSTAT3). Results The PSPCs cell viability was reduced after treated with BBI608 at a lower concentration. Western blot results showed a reduction trend of pSTAT3 after PSPCs treated with BBI608. Our results demonstrated that BBI608 at the certain concentrations worked well in reducing the cell viability of PSPC from the patients who suffered from cervical cancer and endometrial cancer. Conclusions In this study, the patient-specific primary cell (PSPC) was used as the pre-clinical model for investigating the efficiency of BBI608 in reducing cancer cells viability. BBI608, at a clinical-relevant concentration, had valid efficiency in PSPCs from the patients. The dose of drugs treatment and the measured results were more valuable for further guiding clinical trials (AU)

STAT3 inhibitor BBI608 reduces patient-specific primary cell viability of cervical and endometrial cancer at a clinical-relevant concentration.

PURPOSE: Aberrant activation of STAT3 signal pathway promotes tumor progression in many solid tumor types, including cervical cancer and endometrial cancer. BBI608, the STAT3 inhibitor had been reported in previous studies for restraining cancer stem cells. However, whether BBI608 is available for inhibiting the proliferation of cervical cancer or endometrial cancer remains poorly understood. This study investigated the anti-tumor effect and molecular mechanism of BBI608 on the patient-specific primary cells (PSPC) generated from cervical and endometrial cancer in vitro. METHODS: PSPCs were obtained from four patients via biopsy. The cell viability was analyzed by the CCK8 assay. The PSPCs were treated with various concentrations of BBI608 or/and paclitaxel; and then, western blot was applied to investigate the expression of phosphorylated STAT3 (pSTAT3). RESULTS: The PSPCs cell viability was reduced after treated with BBI608 at a lower concentration. Western blot results showed a reduction trend of pSTAT3 after PSPCs treated with BBI608. Our results demonstrated that BBI608 at the certain concentrations worked well in reducing the cell viability of PSPC from the patients who suffered from cervical cancer and endometrial cancer. CONCLUSIONS: In this study, the patient-specific primary cell (PSPC) was used as the pre-clinical model for investigating the efficiency of BBI608 in reducing cancer cells viability. BBI608, at a clinical-relevant concentration, had valid efficiency in PSPCs from the patients. The dose of drugs treatment and the measured results were more valuable for further guiding clinical trials.

Negligible role for pneumococcal surface protein A (PspA) and pneumococcal surface protein C (PspC) in the nasopharyngeal colonization of mice with a serotype 6B pneumococcal strain

Streptococcus pneumoniae colonizes the human nasopharynx asymptomatically, but it can also cause several diseases, including otitis media, pneumonia, bacteremia, and meningitis. The colonization of the nasopharynx by the bacteria is an essential step for the pneumococcus to invade other sites and cause diseases. Pneumococcal surface protein A (PspA) and Pneumococcal surface Protein C (PspC) are important virulence factors and have been described to play roles in adhesion and immune evasion. In this study, we immunized mice subcutaneously with the recombinant α-helical region of PspA and/or PspC combined with different adjuvants to assess protection against colonization with the serotype 6B strain BHN418. Though high serum levels of specific IgG were detected, none of the formulations led to reduction in the colonization of the nasopharynx. The negative result may be due to the poor induction of IgG2c, which has been previously correlated with protection against pneumococcal colonization in mice. Furthermore, BHN418 pspA and pspC single and double knockouts were evaluated in colonization experiments and no differences in bacterial load were observed. In competition assays with the wild-type strain, borderline to no reduction was observed in the loads of the knockouts. Our results contrast with data from the literature using other pneumococcal strains, showing that the role of PspA and PspC in colonization can vary depending on the background of the knockout strain studied. BHN418 has been selected for its capacity to colonize humans in experimental challenge studies and may have redundant factors that compensate for the lack of PspA and PspC during nasopharyngeal colonization of mice.

Negligible role for pneumococcal surface protein A (PspA) and pneumococcal surface protein C (PspC) in the nasopharyngeal colonization of mice with a serotype 6B pneumococcal strain

Streptococcus pneumoniae colonizes the human nasopharynx asymptomatically, but it can also cause several diseases, including otitis media, pneumonia, bacteremia, and meningitis. The colonization of the nasopharynx by the bacteria is an essential step for the pneumococcus to invade other sites and cause diseases. Pneumococcal surface protein A (PspA) and Pneumococcal surface Protein C (PspC) are important virulence factors and have been described to play roles in adhesion and immune evasion. In this study, we immunized mice subcutaneously with the recombinant α-helical region of PspA and/or PspC combined with different adjuvants to assess protection against colonization with the serotype 6B strain BHN418. Though high serum levels of specific IgG were detected, none of the formulations led to reduction in the colonization of the nasopharynx. The negative result may be due to the poor induction of IgG2c, which has been previously correlated with protection against pneumococcal colonization in mice. Furthermore, BHN418 pspA and pspC single and double knockouts were evaluated in colonization experiments and no differences in bacterial load were observed. In competition assays with the wild-type strain, borderline to no reduction was observed in the loads of the knockouts. Our results contrast with data from the literature using other pneumococcal strains, showing that the role of PspA and PspC in colonization can vary depending on the background of the knockout strain studied. BHN418 has been selected for its capacity to colonize humans in experimental challenge studies and may have redundant factors that compensate for the lack of PspA and PspC during nasopharyngeal colonization of mice.

In silico designing of a novel epitope-based candidate vaccine against Streptococcus pneumoniae with introduction of a new domain of PepO as adjuvant.

BACKGROUND: Streptococcus pneumoniae is the leading reason for invasive diseases including pneumonia and meningitis, and also secondary infections following viral respiratory diseases such as flu and COVID-19. Currently, serotype-dependent vaccines, which have several insufficiency and limitations, are the only way to prevent pneumococcal infections. Hence, it is plain to need an alternative effective strategy for prevention of this organism. Protein-based vaccine involving conserved pneumococcal protein antigens with different roles in virulence could provide an eligible alternative to existing vaccines. METHODS: In this study, PspC, PhtD and PsaA antigens from pneumococcus were taken to account to predict B-cell and helper T-cell epitopes, and epitope-rich regions were chosen to build the construct. To enhance the immunogenicity of the epitope-based vaccine, a truncated N-terminal fragment of pneumococcal endopeptidase O (PepO) was used as a potential TLR2/4 agonist which was identified by molecular docking studies. The ultimate construct was consisted of the chosen epitope-rich regions, along with the adjuvant role (truncated N-PepO) and suitable linkers. RESULTS: The epitope-based vaccine was assessed as regards physicochemical properties, allergenicity, antigenicity, and toxicity. The 3D structure of the engineered construct was modeled, refined, and validated. Molecular docking and simulation of molecular dynamics (MD) indicated the proper and stable interactions between the vaccine and TLR2/4 throughout the simulation periods. CONCLUSIONS: For the first time this work presents a novel vaccine consisting of epitopes of PspC, PhtD, and PsaA antigens which is adjuvanted with a new truncated domain of PepO. The computational outcomes revealed that the suggested vaccine could be deemed an efficient therapeutic vaccine for S. pneumoniae; nevertheless, in vitro and in vivo examinations should be performed to prove the potency of the candidate vaccine.

A TET1-PSPC1-Neat1 molecular axis modulates PRC2 functions in controlling stem cell bivalency.

TET1 maintains hypomethylation at bivalent promoters through its catalytic activity in embryonic stem cells (ESCs). However, TET1 catalytic activity-independent function in regulating bivalent genes is not well understood. Using a proteomics approach, we map the TET1 interactome in ESCs and identify PSPC1 as a TET1 partner. Genome-wide location analysis reveals that PSPC1 functionally associates with TET1 and Polycomb repressive complex-2 (PRC2). We establish that PSPC1 and TET1 repress, and the lncRNA Neat1 activates, bivalent gene expression. In ESCs, Neat1 is preferentially bound to PSPC1 alongside its PRC2 association at bivalent promoters. During the ESC-to-epiblast-like stem cell (EpiLC) transition, PSPC1 and TET1 maintain PRC2 chromatin occupancy at bivalent gene promoters, while Neat1 facilitates the activation of certain bivalent genes by promoting PRC2 binding to their mRNAs. Our study demonstrates a TET1-PSPC1-Neat1 molecular axis that modulates PRC2-binding affinity to chromatin and bivalent gene transcripts in controlling stem cell bivalency.

Phyletic Distribution and Diversification of the Phage Shock Protein Stress Response System in Bacteria and Archaea.

Maintaining cell envelope integrity is of vital importance for all microorganisms. Not surprisingly, evolution has shaped conserved protein protection networks that connect stress perception, transmembrane signal transduction, and mediation of cellular responses upon cell envelope stress. The phage shock protein (Psp) stress response is one such conserved protection network. Most knowledge about the Psp response derives from studies in the Gram-negative model bacterium Escherichia coli, where the Psp system consists of several well-defined protein components. Homologous systems were identified in representatives of the Proteobacteria, Actinobacteria, and Firmicutes. However, the Psp system distribution in the microbial world remains largely unknown. By carrying out a large-scale, unbiased comparative genomics analysis, we found components of the Psp system in many bacterial and archaeal phyla and describe that the predicted Psp systems deviate dramatically from the known prototypes. The core proteins PspA and PspC have been integrated into various (often phylum-specifically) conserved protein networks during evolution. Based on protein domain-based and gene neighborhood analyses of pspA and pspC homologs, we built a natural classification system for Psp networks in bacteria and archaea. We validate our approach by performing a comprehensive in vivo protein interaction study of Psp domains identified in the Gram-positive model organism Bacillus subtilis and found a strong interconnected protein network. Our study highlights the diversity of Psp domain organizations and potentially diverse functions across the plethora of the microbial landscape, thus laying the ground for studies beyond known Psp functions in underrepresented organisms. IMPORTANCE The PspA protein domain is found in all domains of life, highlighting its central role in Psp networks. To date, all insights into the core functions of Psp responses derive mainly from protein network blueprints representing only three bacterial phyla. Despite large overlaps in function and regulation, the evolutionary diversity of Psp networks remains largely elusive. Here, we present an unbiased protein domain- and genomic context-centered approach that describes and classifies Psp systems. Our results suggest so-far-unknown Psp-associated roles with other protein networks giving rise to new functions. We demonstrate the applicability of our approach by dissecting the Psp protein network present in Bacillus subtilis and demonstrate Psp domains working in concert with other cell envelope stress response systems. We find that the Psp-like protein universe reflects a surprising diversity within the bacterial and archaeal microbial world.

Nuclear receptor 4A1 (NR4A1) antagonists target paraspeckle component 1 (PSPC1) in cancer cells.

Paraspeckles compound 1 (PSPC1) is a multifunctional protein that plays an important role in cancer cells, where PSPC1 is a master regulator of pro-oncogenic responses that includes activation of TGFß (TGFß1), TGFß-dependent EMT, and metastasis. The pro-oncogenic activities of PSPC1 closely resembled those observed for the orphan nuclear receptor 4A1 (NR4A1, Nur77) and knockdown of NR4A1 decreased expression of PSPC1 in MDA-MB-231 breast, H1299 lung, and SNU449 liver cancer cells. Similar results were observed in these same cell lines after treatment with bisindole-derived (CDIMs) NR4A1 antagonists. Moreover, PSPC1-dependent regulation of TGFß, genes associated with cancer stem cells and epithelial to mesenchymal transition (EMT) were also downregulated after NR4A1 silencing or treatment of breast, lung, and liver cancer cells with CDIM/NR4A1 antagonists. Results of chromatin immunoprecipitation (ChIP) assays suggest that NR4A1 regulates PSPC1 through interaction with an NBRE sequence in the PSPC1 gene promoter. These results coupled with in vivo studies showing that NR4A1 antagonists inhibit breast tumor growth and downregulate PSPC1 in tumors indicate that the pro-oncogenic nuclear PSPC1 factor can be targeted by CDIM/NR4A1 antagonists.

Effects of Expression of Streptococcus pneumoniae PspC on the Ability of Streptococcus mitis to Evade Complement-Mediated Immunity.

Streptococcus pneumoniae and Streptococcus mitis are genetically closely related and both frequently colonise the naso-oropharynx, yet S. pneumoniae is a common cause of invasive infections whereas S. mitis is only weakly pathogenic. We hypothesise that sensitivity to innate immunity may underlie these differences in virulence phenotype. We compared the sensitivity of S. pneumoniae and S. mitis strains to complement-mediated immunity, demonstrating S. mitis strains were susceptible to complement-mediated opsonophagocytosis. S. pneumoniae resistance to complement is partially dependent on binding of the complement regulator Factor H by the surface protein PspC. However, S. mitis was unable to bind factor H. The S. pneumoniae TIGR4 strain pspC was expressed in the S. mitis SK142 strain to create a S. mitis pspC+ strain. Immunoblots demonstrated the S. mitis pspC+ strain expressed PspC, and flow cytometry confirmed this resulted in Factor H binding to S. mitis, reduced susceptibility to complement and improved survival in whole human blood compared to the wild-type S. mitis strain. However, in mouse models the S. mitis pspC+ strain remained unable to establish persistent infection. Unlike S. pneumoniae strains, culture in serum or blood did not support increased CFU of the S. mitis strains. These results suggest S. mitis is highly sensitive to opsonisation with complement partially due to an inability to bind Factor H, but even when complement sensitivity was reduced by expression of pspC, poor growth in physiological fluid limited the virulence of S. mitis in mice.

PSPC1 regulates CHK1 phosphorylation through phase separation and participates in mouse oocyte maturation.

Liquid-liquid phase separation (LLPS) underlies the formation of membraneless compartments in mammal cells. However, there are few reports that focus on the correlation of mouse oocyte maturation with LLPS. Previous studies have reported that paraspeckle component 1 (PSPC1) is related to the occurrence and development of tumors, but whether PSPC1 functions in mouse oocyte maturation is still unclear. Sequence analysis of PSPC1 protein showed that it contains a prion-like domain (PrLD) that is required for phase separation of proteins. In this study, we found that PSPC1 could undergo phase separation. Moreover, the loss of PrLD domain of PSPC1 could greatly weaken its phase separation ability. The immunofluorescence assays showed that PSPC1 is present in mouse oocytes in the germinal vesicle (GV) stage. Knockdown of PSPC1 significantly impeded the maturation of mouse oocytes in vitro. CHK1 has been reported to play important roles in the GV stage of mouse oocytes. Co-IP experiment revealed that PSPC1 could interact with phosphatase serine/threonine-protein phosphatase 5 (PPP5C), which regulates CHK1 phosphorylation. Western blot analysis revealed that PSPC1 could regulate the phosphorylation of CHK1 through PPP5C; however, PSPC1 without PrLD domain was inactive, suggesting that the lack of phase separation ability led to the abnormal function of PSPC1 in regulating CHK1 phosphorylation. Thus, we conclude that PSPC1 may undergo phase separation to regulate the phosphorylation level of CHK1 via PPP5C and participate in mouse oocyte maturation. Our study provides new insights into the mechanism of mouse oocyte maturation.

PSPC1 is a new contextual determinant of aberrant subcellular translocation of oncogenes in tumor progression.

Dysregulation of nucleocytoplasmic shuttling is commonly observed in cancers and emerging as a cancer hallmark for the development of anticancer therapeutic strategies. Despite its severe adverse effects, selinexor, a selective first-in-class inhibitor of the common nuclear export receptor XPO1, was developed to target nucleocytoplasmic protein shuttling and received accelerated FDA approval in 2019 in combination with dexamethasone as a fifth-line therapeutic option for adults with relapsed refractory multiple myeloma (RRMM). To explore innovative targets in nucleocytoplasmic shuttling, we propose that the aberrant contextual determinants of nucleocytoplasmic shuttling, such as PSPC1 (Paraspeckle component 1), TGIF1 (TGF-ß Induced Factor Homeobox 1), NPM1 (Nucleophosmin), Mortalin and EBP50, that modulate shuttling (or cargo) proteins with opposite tumorigenic functions in different subcellular locations could be theranostic targets for developing anticancer strategies. For instance, PSPC1 was recently shown to be the contextual determinant of the TGF-ß prometastatic switch and PTK6/ß-catenin reciprocal oncogenic nucleocytoplasmic shuttling during hepatocellular carcinoma (HCC) progression. The innovative nucleocytoplasmic shuttling inhibitor PSPC1 C-terminal 131 polypeptide (PSPC1-CT131), which was developed to target both the shuttling determinant PSPC1 and the shuttling protein PTK6, maintained their tumor-suppressive characteristics and exhibited synergistic effects on tumor suppression in HCC cells and mouse models. In summary, targeting the contextual determinants of nucleocytoplasmic shuttling with cargo proteins having opposite tumorigenic functions in different subcellular locations could be an innovative strategy for developing new therapeutic biomarkers and agents to improve cancer therapy.

The Prognosis Value of PSPC1 Expression in Nasopharyngeal Cancer.

BACKGROUND: Paraspeckle component 1 (PSPC1) is overexpressed in various cancer and correlated with poor survival in the patients. However, little is known about its expression and role in the progression of nasopharyngeal carcinomas (NPC). The purpose of this study is to examine PSPC1 expression in NPC and explore its role in clinical prognosis of radiation therapy. METHODS: The association of PSPC1 expression with clinicopathological features of 109 NPC patients was examined using partial correlation analysis. Cancer tissues were obtained prior to clinical treatment. All cases were diagnosed and pathologically confirmed to be poorly differentiated or undifferentiated NPC without distant metastasis. The patients were then treated with radiation and followed-up. Survival analysis was performed. RESULTS: Partial correlation analysis revealed that the PSPC1 expression in NPC was correlated with N classification, recurrence, prognosis and radiosensitivity in NPC patients, but not with the gender, age, pathohistological pattern, clinical stage, and T classification. The overexpression of PSPC1 was detected in 64 samples (58.72%). Kaplan-Meier survival analysis revealed that the overall survival (OS) was longer in NPC patients with PSPC1 low expression than that in those with PSPC1 high expression. Moreover, patients with the overexpression of PSPC1 had a low progression-free survival and distant metastasis-free survival rate, compared to those who had a low expression of PSPC1. Although not statistically significant, patients with high expression of PSPC1 had a lower locoregional recurrence-free survival rate than those with low expression, and the curves between the two groups was well separated. CONCLUSION: PSPC1 overexpression was associated with poor prognosis for NPC, which might be a novel useful biomarker to predict the response of NPC to radiation therapy and its clinical outcome.