E3 Ubiquitin Ligase Riplet Is Expressed in T Cells and Suppresses T Cell-Mediated Antitumor Immune Responses

K63-linked polyubiquitination of LGP2 by Riplet regulates RIG-I-dependent innate immune response

Type I interferons (IFNs) exhibit strong antiviral activity and induce the expression of antiviral proteins. Since excessive expression of type I IFNs is harmful to the host, their expression should be turned off at the appropriate time. In this study, we find that post-translational modification of LGP2, a member of the RIG-I-like receptor family, modulates antiviral innate immune responses. The LGP2 protein undergoes K63-linked polyubiquitination in response to cytoplasmic double-stranded RNAs or viral infection. Our mass spectrometry analysis reveals the K residues ubiquitinated by the Riplet ubiquitin ligase. LGP2 ubiquitination occurs with a delay compared to RIG-I ubiquitination. Interestingly, ubiquitination-defective LGP2 mutations increase the expression of type I IFN at a late phase, whereas the mutant proteins attenuate other antiviral proteins, such as SP100, PML, and ANKRD1. Our data indicate that delayed polyubiquitination of LGP2 fine-tunes RIG-I-dependent antiviral innate immune responses at a late phase of viral infection.

Circulating tumour cell combined with DNA methylation for early detection of hepatocellular carcinoma

Background: The inadequate early detection strategies makes hepatocellular carcinoma (HCC) patients with poor prognisis. Therefore, more effective detection methods are urgently needed for early detection and early intervention of HCC. Methods: 17 cases of suspected HCC patients and 11 cases of HBV-related decompensated cirrhosis (HBV-DeCi) patients were enrolled. For each patient, 5 ml blood sample was separated into circulating tumor cells (CTCs) and plasma, CTCs were stained with Diff staining for counting. Plasma was used for extracting cell free DNA (cfDNA) and then analyzed by qMSP assay. Ct values were recorded for GNB4 and Riplet as target genes and β-actin as an endogenous reference gene. Finally, clinical efficacy of CTC count combined with GNB4/Riplet methylation detection for early diagnosis of HCC was analyzed. Results: The CTC of HCC patients has pleomorphic characteristics, but it is difficult to distinguish from other blood cells with non-obviously pleomorphic of CTC. Although a small number of CTCs can also be detected in HBV-DeCi patients (control group), the number is significantly lower than that in HCC patients, the sensitivity and specificity of CTC for HCC detection were 70.6% and 90.9% (AUC = 0.81). The Ct values of GNB4 and Riplet methylation were significantly different between HCC patients and control group patients. When CTC combined with two genes, the AUC value was significantly increased to 0.98, the sensitivity was 88.2%, and the specificity was 100%. Conclusion: Our study has developed a novel test that CTC count combined with GNB4/Riplet methylation detection and showed its high performance for early diagnosis of HCC.

Comprehensive Characterization of a Novel E3-Related Gene Signature With Implications in Prognosis and Immunotherapy of Low-Grade Gliomas

Gliomas, a type of primary brain tumor, have emerged as a threat to global mortality due to their high heterogeneity and mortality. A low-grade glioma (LGG), although less aggressive compared with glioblastoma, still exhibits high recurrence and malignant progression. Ubiquitination is one of the most important posttranslational modifications that contribute to carcinogenesis and cancer recurrence. E3-related genes (E3RGs) play essential roles in the process of ubiquitination. Yet, the biological function and clinical significance of E3RGs in LGGs need further exploration. In this study, differentially expressed genes (DEGs) were screened by three differential expression analyses of LGG samples from The Cancer Genome Atlas (TCGA) database. DEGs with prognostic significance were selected by the univariate Cox regression analysis and log-rank statistical test. The LASSO-COX method was performed to identify an E3-related prognostic signature consisting of seven genes AURKA, PCGF2, MAP3K1, TRIM34, PRKN, TLE3, and TRIM17. The Chinese Glioma Genome Atlas (CGGA) dataset was used as the validation cohort. Kaplan–Meier survival analysis showed that LGG patients in the low-risk group had significantly higher overall survival time than those in the high-risk group in both TCGA and CGGA cohorts. Furthermore, multivariate Cox regression analysis revealed that the E3RG signature could be used as an independent prognostic factor. A nomogram based on the E3RG signature was then established and provided the prediction of the 1-, 3-, and 5-year survival probability of patients with LGGs. Moreover, DEGs were analyzed based on the risk signature, on which function analyses were performed. GO and KEGG analyses uncovered gene enrichment in extracellular matrix–related functions and immune-related biological processes in the high-risk group. GSEA revealed high enrichment in pathways that promote tumorigenesis and progression in the high-risk group. Furthermore, ESTIMATE algorithm analysis showed a significant difference in immune and stroma activity between high- and low-risk groups. Positive correlations between the risk signature and the tumor microenvironment immune cell infiltration and immune checkpoint molecules were also observed, implying that patients with the high-risk score may have better responses to immunotherapy. Overall, our findings might provide potential diagnostic and prognostic markers for LGG patients and offer meaningful insight for individualized treatment.