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Several decades after the discovery of the human norovirus, with thousands of lives and billions of dollars lost, the lack of a robust cell culture system still severely hampers development of vaccines and therapeutics. This is likely in large part as a result of our limited understanding of the immune responses against an infection with the virus. Here, the presence of a RIG-I/STING-dependent innate response pathway that restricts the replication of noroviruses is described, and an attempt by the murine norovirus to subvert it through expression of an accessory protein is demonstrated. We show that both RIG-I and STING are required for a robust interferon response to infection with MNV1 in primary BMDMs and RAW264.7 cells, with a significant increase in viral titres following infection in RIG-I- and STING-deficient cells. We also show that STING is non-canonically activated in MNV1-infected cells partly in a RIG-I dependent manner. Furthermore, our data indicate that the MNV VF1 protein binds to STING and can inhibit interferon induction downstream of RIG-I. Secondly, while exploring the mechanisms for the differential induction of interferon sub- types, we show that depletion of MED23 leads to a reduction in expression of both types I and III IFNs in human and mouse cell lines. We also show that Med23 knockout cells undergo genetic compensation, suggesting a critical role for MED23 in this pathway. Mechanistically, we show that MED23 interacts with IRF3, and is required for recruitment of RNA Polymerase II to promoters of IRF3-dependent genes. Taken together, our data indicate that MED23 plays a central role in antiviral responses by coupling IRF3 activation and RNA Pol II recruitment., Presidential Special Scholarship Scheme for Innovation and Development (Nigerian Government)

We investigated the role of the transcriptional mediator subunit 23 (MED23) in everolimus drug resistance, invasion and metastasis during breast cancer treatment and its molecular mechanism. We also evaluated the endocrinotherapy and prevention method for breast cancer. Breast cancer cell strains were established that can continuously express MED23, as well as inducible MED23-shRNA expression plasmids. The inductive agent, doxycycline (Dox), was added to the water for long-term silencing of MED23 in intratumoral cells. We conducted experiments on the role of MED23 in the regulation of invasion and metastasis of breast cancer using cell culture, western blotting, MTT proliferation experiment, fluorescent quantitative PCR and chromatin immunoprecipitation (ChIP). The silencing of MED23 significantly inhibited cellular growth and proliferation as well as soft agar cloning. Silencing of MED23 strengthened the sensitivity of the everolimus-resistant breast cancer cell strains BT474 and MCF-7/ADM cells to everolimus medication. The silencing of MED23, in combination with everolimus, inhibits the cell cycle progress of breast cancer cells. ChIP indicated that the mutual regulation of HER2 and MED23 also participates in the formation of the everolimus drug resistance mechanism. Therefore, MED23 plays an important role in everolimus drug resistance, invasion, and metastasis of breast cancer. As a potential molecular therapeutic target of breast cancer, MED23 overcomes drug resistance in clinical endocrinotherapy and controls the distal relapse and metastasis in breast cancer by the targeted silencing of MED23.

DNA repair is related to many physiological and pathological processes, including pigmentation. Little is known about the role of the transcriptional cofactor Mediator complex in DNA repair and pigmentation. Here, we demonstrate that Mediator MED23 plays an important role in coupling UV-induced DNA repair to pigmentation. The loss of Med23 specifically impairs the pigmentation process in melanocyte-lineage cells and in zebrafish. Med23 deficiency leads to enhanced nucleotide excision repair (NER) and less DNA damage following UV radiation because of the enhanced expression and recruitment of NER factors to chromatin for genomic stability. Integrative analyses of melanoma cells reveal that MED23 controls the expression of a melanocyte master regulator, Mitf, by modulating its distal enhancer activity, leading to opposing effects on pigmentation and DNA repair. Collectively, the Mediator MED23/MITF axis connects DNA repair to pigmentation, thus providing molecular insights into the DNA damage response and skin-related diseases.