Ribosomal L1 domain and lysine-rich region are essential for CSIG/ RSL1D1 to regulate proliferation and senescence

Karyopherin α deficiency contributes to human preimplantation embryo arrest

Preimplantation embryo arrest (PREMBA) is a common cause of female infertility and recurrent failure of assisted reproductive technology. However, the genetic basis of PREMBA is largely unrevealed. Here, using whole-exome sequencing data from 606 women experiencing PREMBA compared with 2,813 controls, we performed a population and gene-based burden test and identified a candidate gene, karyopherin subunit α7 (KPNA7). In vitro studies showed that identified sequence variants reduced KPNA7 protein levels, impaired KPNA7 capacity for binding to its substrate ribosomal L1 domain-containing protein 1 (RSL1D1), and affected KPNA7 nuclear transport activity. Comparison between humans and mice suggested that mouse KPNA2, rather than mouse KPNA7, acts as an essential karyopherin in embryonic development. Kpna2-/- female mice showed embryo arrest due to zygotic genome activation defects, recapitulating the phenotype of human PREMBA. In addition, female mice with an oocyte-specific knockout of Rsl1d1 recapitulated the phenotype of Kpna2-/- mice, demonstrating the vital role of substrate RSL1D1. Finally, complementary RNA (cRNA) microinjection of human KPNA7, but not mouse Kpna7, was able to rescue the embryo arrest phenotype in Kpna2-/- mice, suggesting mouse KPNA2 might be a homologue of human KPNA7. Our findings uncovered a mechanistic understanding for the pathogenesis of PREMBA, which acts by impairing nuclear protein transport, and provide a diagnostic marker for PREMBA patients.

RSL1D1 modulates cell senescence and proliferation via regulation of PPARγ mRNA stability

AIMS

In this study, we will examine if RSL1D1 influences PPARγ expression and explore the underlying mechanism that RSL1D1 regulates PPARγ expression. Moreover, the significance of RSL1D1-PPARγ pathway in cell senescence and proliferation will also be determined.

MAIN METHODS

Our main methods include western blotting, immunoprecipitation (IP), real-time PCR, RNA Immunoprecipitation (RIP), biotin-labeled RNA pull down assay, dual luciferase reporter gene assay, senescence-associated β-galactosidase staining, cell proliferation assay, colony formation assay, wound healing assay, blood biochemistry test and Oil red O staining.

KEY FINDINGS

By analyzing gene chip results we find that the expression of RSL1D1 and PPARγ might be correlated. Then we show that RSL1D1 is a posttranscriptional regulator of PPARγ. RSL1D1 overexpression elevates, while RSL1D1 knockdown inhibits, PPARγ mRNA and protein expression levels. Mechanistically, we find that RSL1D1 directly interacts with the 3'-untranslated region of PPARγ mRNA, and then promotes its stability and increases PPARγ protein expression level. We further demonstrate that RSL1D1 modulates cellular senescence and cell proliferation partially via PPARγ-regulated downstream target genes such as PTEN/p27, NF-κB, GLUT4, and ACL. Moreover, we find that RSL1D1 regulates PPARγ expression and function in a HuR-dependent manner. Last, we show that RSL1D1 knockout in mouse adipose tissue shortens mouse lifespan and leads to hepatic damage which may impair liver damage repair function.

SIGNIFICANCE

Collectively, our findings unveil a novel posttranscriptional regulation of PPARγ by RSL1D1 and uncover a critical role of RSL1D1-PPARγ-PPARγ downstream target genes in regulating cellular senescence and cell proliferation.

Bioinformatics analyses of potential ACLF biological mechanisms and identification of immune-related hub genes and vital miRNAs

Acute-on-chronic liver failure (ACLF) is a critical and refractory disease and a hepatic disorder accompanied by immune dysfunction. Thus, it is essential to explore key immune-related genes of ACLF and investigate its mechanisms. We used two public datasets (GSE142255 and GSE168048) to perform various bioinformatics analyses, including WGCNA, CIBERSORT, and GSEA. We also constructed an ACLF immune-related protein-protein interaction (PPI) network to obtain hub differentially expressed genes (DEGs) and predict corresponding miRNAs. Finally, an ACLF rat model was established to verify the results. A total of 388 DEGs were identified in ACLF, including 162 upregulated and 226 downregulated genes. The enrichment analyses revealed that these DEGs were mainly involved in inflammatory-immune responses and biosynthetic metabolic pathways. Twenty-eight gene modules were obtained using WGCNA and the coral1 and darkseagreen4 modules were highly correlated with M1 macrophage polarization. As a result, 10 hub genes and 2 miRNAs were identified to be significantly altered in ACLF. The bioinformatics analyses of the two datasets presented valuable insights into the pathogenesis and screening of hub genes of ACLF. These results might contribute to a better understanding of the potential molecular mechanisms of ACLF. Finally, further studies are required to validate our current findings.

Mutations in DNA binding domain of p53 impede RSL1D1-p53 interaction to escape from degradation in human colorectal cancer cells

Different from the nucleolus-specific localization in some types of cancer cells, ribosomal L1 domain-containing protein 1 (RSL1D1) distributes throughout the nucleus in human colorectal cancer (CRC) cells. RSL1D1 directly interacts with DNA binding domain (aa 93-292) of wild-type p53 (p53-WT) and thereby recruits p53 to HDM2. The ensuing formation of RSL1D1/HDM2/p53 complex enhances p53 ubiquitination and decreases the protein level of p53 in CRC cells. In this study, we investigated the interaction between RSL1D1 and mutant p53 proteins. We first corroborated that aa 93-224 of p53 is a more precise domain for RSL1D1 binding and mutation in either aa 93-224 or aa 225-292 domain of p53 affects RSL1D1-p53 interaction. R175H mutated p53 does not interact with RSL1D1, whereas R273H mutated p53 still can bind to RSL1D1 but showing a remarkably decreased affinity than p53-WT. Although p53-R273H retained a weakened binding affinity with RSL1D1, it can hardly be recruited to HDM2 by RSL1D1 in HCT116 CRC cells. Accordingly, RSL1D1 lost its capacity to negatively regulate either R175H or R273H p53 mutant via directly interaction in HCT116 cells, thereby facilitating p53 mutants to accumulate and gain oncogenic function. Our findings help explain why mutant p53 proteins are more stable than p53-WT in CRC cells.

Ribosomal L1 domain-containing protein 1 coordinates with HDM2 to negatively regulate p53 in human colorectal Cancer cells

BACKGROUND

Ribosomal L1 domain-containing protein 1 (RSL1D1) is a nucleolar protein that is essential in cell proliferation. In the current opinion, RSL1D1 translocates to the nucleoplasm under nucleolar stress and inhibits the E3 ligase activity of HDM2 via direct interaction, thereby leading to stabilization of p53.

METHODS

Gene knockdown was achieved in HCT116^p53+/+, HCT116^p53-/-, and HCT-8 human colorectal cancer (CRC) cells by siRNA transfection. A lentiviral expression system was used to establish cell strains overexpressing genes of interest. The mRNA and protein levels in cells were evaluated by qRT-PCR and western blot analyses. Cell proliferation, cell cycle, and cell apoptosis were determined by MTT, PI staining, and Annexin V-FITC/PI double staining assays, respectively. The level of ubiquitinated p53 protein was assessed by IP. The protein-RNA interaction was investigated by RIP. The subcellular localization of proteins of interest was determined by IFA. Protein-protein interaction was investigated by GST-pulldown, BiFC, and co-IP assays. The therapeutic efficacy of RSL1D1 silencing on tumor growth was evaluated in HCT116 tumor-bearing nude mice.

RESULTS

RSL1D1 distributed throughout the nucleus in human CRC cells. Silencing of RSL1D1 gene induced cell cycle arrest at G1/S and cell apoptosis in a p53-dependent manner. RSL1D1 directly interacted with and recruited p53 to HDM2 to form a ternary RSL1D1/HDM2/p53 protein complex and thereby enhanced p53 ubiquitination and degradation, leading to a decrease in the protein level of p53. Destruction of the ternary complex increased the level of p53 protein. RSL1D1 also indirectly decreased the protein level of p53 by stabilizing HDM2 mRNA. Consequently, the negative regulation of p53 by RSL1D1 facilitated cell proliferation and survival and downregulation of RSL1D1 remarkably inhibited the growth of HCT116^p53+/+ tumors in a nude mouse model.

CONCLUSION

We report, for the first time, that RSL1D1 is a novel negative regulator of p53 in human CRC cells and more importantly, a potential molecular target for anticancer drug development.

Proteome Analysis in PAM Cells Reveals That African Swine Fever Virus Can Regulate the Level of Intracellular Polyamines to Facilitate Its Own Replication through ARG1

In 2018, African swine fever broke out in China, and the death rate after infection was close to 100%. There is no effective and safe vaccine in the world. In order to better characterize and understand the virus–host-cell interaction, quantitative proteomics was performed on porcine alveolar macrophages (PAM) infected with ASFV through tandem mass spectrometry (TMT) technology, high-performance liquid chromatography (HPLC), and mass spectrometry (MS). The proteome difference between the simulated group and the ASFV-infected group was found at 24 h. A total of 4218 proteins were identified, including 306 up-regulated differentially expressed proteins and 238 down-regulated differentially expressed proteins. Western blot analysis confirmed changes in the expression level of the selected protein. Pathway analysis is used to reveal the regulation of protein and interaction pathways after ASFV infection. Functional network and pathway analysis can provide an insight into the complexity and dynamics of virus–host cell interactions. Further study combined with proteomics data found that ARG1 has a very important effect on ASFV replication. It should be noted that the host metabolic pathway of ARG1-polyamine is important for virus replication, revealing that the virus may facilitate its own replication by regulating the level of small molecules in the host cell.

Downregulation of circ_0000673 Promotes Cell Proliferation and Migration in Endometriosis via the Mir-616-3p/PTEN Axis

Endometriosis is a common gynecological disease, affecting up to 10% of women of reproductive age and approximately 50% of women with infertility. Circular RNAs (circRNAs) have been shown to be involved in a number of diseases. Dysregulated expression of circRNAs in endometriosis has been reported, and circ_0000673 was significantly downregulated. However, the details of its role in the pathogenesis of endometriosis are still poorly understood. We investigated the location and effects of the downregulation of circ_0000673 in endometriosis. We demonstrated that knockdown of circ_0000673 significantly increased the proliferation and migration of eutopic and normal endometrial cells. Bioinformatics analysis predicted that circ_0000673 might act as a sponge for miR-616-3p. We found that the effect of circ_0000673 knockdown could be recovered by miR-616-3p inhibitor and enhanced by miR-616-3p mimics. qPCR and western blot assays showed that circ_0000673 knockdown could decrease the expression of PTEN and increase the expression of PI3K and p-AKT. PTEN was confirmed to be a target of miR-616-3p. These results demonstrated that the downregulation of circ_0000673 could promote the progression of endometriosis by inactivating PTEN via the deregulation of miR-616-3p.

Circular RNA as a potential diagnostic and/or therapeutic target for endometriosis

Endometriosis is a pathology form of endometrium that behaves in a similar way to malignancies, such as invasion and resistance to apoptosis. Circular RNAs (CircRNAs) are a class of noncoding RNAs that have several biological functions including, miRNA sponging, sequestering of proteins, enhancing parental gene expression and translation resulting in polypeptides. In this review, we highlighted the roles of circRNAs as potential diagnostic and therapeutic biomarkers in endometriosis. Moreover, we summarized the roles of circRNAs in the pathogenesis of endometriosis via different signaling pathways, such as the miRNA network and apoptosis.

The Cellular Senescence-Inhibited Gene Is Essential for PPM1A Myristoylation To Modulate Transforming Growth Factor β Signaling

The cellular senescence-inhibited gene (CSIG) is implicated in important biological processes, including cellular senescence and apoptosis. Our work showed that CSIG is involved in the myristoylation of the serine/threonine protein phosphatase PPM1A. Previous research has shown that myristoylation is necessary for PPM1A to dephosphorylate Smad2 and Smad3. However, the control and the biological significance of the myristoylation remain poorly understood. In this study, we found that CSIG knockdown disturbs PPM1A myristoylation and reduces the dephosphorylation by PPM1A of its substrate Smad2. By regulating PPM1A myristoylation, CSIG is involved in modulating the signaling of transforming growth factor β (TGF-β). Further study of the mechanism indicated that CSIG facilitates the interaction between N-myristoyltransferase 1 (NMT1) and PPM1A. Taking the data together, we found that CSIG is a regulator of PPM1A myristoylation and TGF-β signaling. By promoting the myristoylation of PPM1A, CSIG enhanced the phosphatase activity of PPM1A and further inhibited TGF-β signaling. This work not only extends the biological significance of CSIG but also provides new ideas and a reference for the study of the regulatory mechanism of myristoylation.

Circular RNA expression in ovarian endometriosis

AIM

Circular RNAs (circRNAs) with miRNA response elements (MREs) could function as competing endogenous RNA (ceRNA) in regulating gene expression. This study was carried out to identify the expression profile and role of circRNAs in endometriosis.

MATERIALS & METHODS

Microarray assay was performed in four paired ovarian endometriomas and eutopic endometrium, followed by quantitative real-time RT-PCR in 24 paired samples. Bioinformatical algorithms were used to predict MREs, as well as ceRNA and KEGG pathway analysis.

RESULTS

We identified 262 upregulated and 291 downregulated circRNAs, binding with 1225 MREs. The ceRNA network included 122 miRNAs and 137 mRNAs, which are involed in nine pathways.

CONCLUSION

CircRNAs are differentially expressed in endometriosis, which might be related with pathogenesis of endometriosis.

Regulation of the MDM2-p53 pathway by the nucleolar protein CSIG in response to nucleolar stress

Nucleolar proteins play an important role in the regulation of the MDM2-p53 pathway, which coordinates cellular response to stress. However, the mechanism underlying this regulation remains poorly understood. Here, we report that the nucleolar protein CSIG is a novel and crucial regulator of the MDM2-p53 pathway. We demonstrate that CSIG translocates from the nucleolus to the nucleoplasm in response to nucleolar stress. Moreover, knockdown of CSIG attenuates the induction of p53 and abrogates G1 phase arrest in response to nucleolar stress. CSIG interacts directly with the MDM2 RING finger domain and inhibits MDM2 E3 ubiquitin ligase activity, thus resulting in a decrease in MDM2-mediated p53 ubiquitination and degradation. Our results suggest that the CSIG-MDM2-p53 regulatory pathway plays an important role in the cellular response to nucleolar stress.