SERTAD1 initiates NLRP3-mediated inflammasome activation through restricting NLRP3 polyubiquitination

We here demonstrate that SERTAD1 is an adaptor protein responsible for the regulation of lysine 63 (K63)-linked NLRP3 polyubiquitination by the Cullin1 E3 ubiquitin ligase upon inflammasome activation. SERTAD1 specifically binds to NLRP3 but not to other inflammasome sensors. This endogenous interaction increases after inflammasome activation, interfering with the interaction between NLRP3 and Cullin1. Interleukin (IL)-1β and IL-18 secretion, as well as the cleavage of gasdermin D, are decreased in SERTAD1 knockout bone-marrow-derived macrophages, together with reduced formation of the NLRP3 inflammasome complex. Additionally, SERTAD1-deficient mice show attenuated severity of monosodium-uric-acid-induced peritonitis and experimental autoimmune encephalomyelitis. Analysis of public datasets indicates that expression of SERTAD1 mRNA is significantly increased in the patients of autoimmune diseases. Thus, our findings uncover a function of SERTAD1 that specifically reduces Cullin1-mediated NLRP3 polyubiquitination via direct binding to NLRP3, eventually acting as a crucial factor to regulate the initiation of NLRP3-mediated inflammasome activation.

SERTA Domain Containing Protein 1 (SERTAD1) Interacts with Classical Swine Fever Virus Structural Glycoprotein E2, Which Is Involved in Virus Virulence in Swine

E2 is the major structural glycoprotein of the classical swine fever virus (CSFV). E2 has been shown to be involved in important virus functions such as replication and virulence in swine. Using the yeast two-hybrid system, we previously identified several host proteins specifically interacting with CSFV E2. Here, we analyze the protein interaction of E2 with SERTA domain containing protein 1 (SERTAD1), a factor involved in the stimulation of the transcriptional activities of different host genes. We have confirmed that the interaction between these two proteins occurs in CSFV-infected swine cells by using a proximity ligation assay and confocal microscopy. Amino acid residues in the CSFV E2 protein that are responsible for mediating the interaction with SERTAD1 were mapped by a yeast two-hybrid approach using a randomly mutated E2 library. Using that information, a recombinant CSFV mutant (E2ΔSERTAD1v) that harbors substitutions in those residues mediating the protein-interaction with SERTAD1 was developed and used to study the role of the E2-SERTAD1 interaction in viral replication and virulence in swine. CSFV E2ΔSERTAD1v, when compared to the parental BICv, showed a clearly decreased ability to replicate in the SK6 swine cell line and a more severe replication defect in primary swine macrophage cultures. Importantly, 80% of animals infected with E2ΔSERTAD1v survived infection, remaining clinically normal during the 21-day observational period. This result would indicate that the ability of CSFV E2 to bind host SERTAD1 protein during infection plays a critical role in virus virulence.

Prognostic and Clinicopathological Significance of SERTAD1 in Various Types of Cancer Risk: A Systematic Review and Retrospective Analysis

SERTAD/TRIP-Br genes are considered as a key nuclear transcriptional player in diverse mechanisms of cell including carcinogenesis. The Oncomine™-Online Platform was used for differential expression and biological insights. Kaplan-Meier survival estimated by KM-plotter/cBioPortal/PrognoScan with 95% CI. SERTAD1 was found significantly elevated levels in most of tumor samples. Kaplan-Meier Plotter results distinctly showed the SERTAD1 over-expression significantly reduced median overall-survival (OS) of patients in liver (n = 364/Logrank-test p = 0.0015), ovarian (n = 655/Logrank-test p = 0.00011) and gastric (n = 631/Logrank-test p = 0.1866). Increased level of SERTAD1 has a significantly higher survival rate in the initial time period, but after 100 months slightly reduced OS (n = 26/Logrank-test p = 0.34) and RFS in HER2 positive breast cancer patients. In meta-analysis, cancer patients with higher SERTAD1 mRNA fold resulted worse overall survival than those with lower SERTAD1 levels. Heterogeneity was observed in the fixed effect model analysis DFS [Tau² = 0.0.073, Q (df = 4) = 15.536 (p = 0.004), I² = 74.253], DSS [Tau² = 1.015, Q (df = 2) = 33.214, (p = 0.000), I² = 93.973], RFS [Tau² = 0.492, Q (df = 7) = 71.133 (p = 0.000), I² = 90.159] (Figure 5). OS [Tau² = 0.480, Q (df = 17) = 222.344 (p = 0.000), I² = 92.354]. Lastly, SERTAD1 involved in several signaling cascades through interaction and correlation with many candidate factors as well as miRNAs. This meta-analysis demonstrates a robust evidence of an association between higher or lower SERTAD1, alteration and without alteration of SERTAD1 in cancers in terms of survival and cancer invasiveness.

SEI1 induces genomic instability by inhibiting DNA damage response in ovarian cancer

Previous studies have shown that the oncogene SEI1 is highly expressed in ovarian carcinomas, and promoting genomic instability. However, the molecular mechanism of SEI1 in promoting genomic instability remains unclear. We observed SEI1 overexpression in 30 of 46 cases of ovarian cancer compared to non-tumor tissues and the overexpression of SEI1 was positively associated with the tumor FIGO stage. Our functional studies revealed that overexpression of SEI1 could induce genomic instability and increased DNA strand breaks. In contrast, SEI1 co-localized with γH2AX and phosphorylated ATM and DNAPKcs in the nucleus. Furthermore, we found that overexpression of SEI1 induced translocation of the SEI1 protein from the cytoplasm to the nucleus; ATM and DNAPKcs were associated with the cytoplasm-to-nucleus translocation of SEI1. To further prove the correlation between the DNA damage response (DDR) and SEI1, we knocked down SEI1 expression in SEI1-transfected ovarian cancer cell lines. The expression of DDR proteins was significantly downregulated, and the number of micronuclei was significantly decreased. Together, these results define a new mechanism of SEI1 in the regulation of genomic stability and in the malignant progression of ovarian cancer.