RNF6 promotes the migration and invasion of breast cancer by promoting the ubiquitination and degradation of MST1

Proteasomal down-regulation of the proapoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

The loss of MST2 pathway protein expression in BRAF inhibitor resistant melanoma cells is due to ubiquitination and subsequent proteasomal degradation and prevents MST2-mediated apoptosis.

The RAS-RAF-MEK-ERK pathway is hyperactivated in most malignant melanomas, and mutations in BRAF or NRAS account for most of these cases. BRAF inhibitors (BRAFi) are highly efficient for treating patients with BRAF^V600E mutations, but tumours frequently acquire resistance within a few months. Multiple resistance mechanisms have been identified, due to mutations or network adaptations that revive ERK signalling. We have previously shown that RAF proteins inhibit the MST2 proapoptotic pathway in a kinase-independent fashion. Here, we have investigated the role of the MST2 pathway in mediating resistance to BRAFi. We show that the BRAF^V600E mutant protein, but not the wild-type BRAF protein, binds to MST2 inhibiting its proapoptotic signalling. Down-regulation of MST2 reduces BRAFi-induced apoptosis. In BRAFi-resistant cell lines, MST2 pathway proteins are down-regulated by ubiquitination and subsequent proteasomal degradation rendering cells refractory to MST2 pathway–induced apoptosis. Restoration of apoptosis can be achieved by increasing MST2 pathway protein expression using proteasome inhibitors. In summary, we show that the MST2 pathway plays a role in the acquisition of BRAFi resistance in melanoma.

E3 ubiquitin ligase RNF6 promotes antiviral immune responses through enhancing the expression of interferon stimulated genes in myeloid cells

Interferon signaling is closely associated with clearance of viral infections as well as the development of systemic lupus erythematosus (SLE). Therefore, from a clinical perspective, it is important to identify the key regulators involved in interferon signaling pathways. In this study, we identified that RNF6, as an interferon inducible E3 ubiquitin ligase, promoted the interferon-dependent antiviral response. Knock-down of RNF6 greatly attenuated expression of ISGs and the transcriptional activity of ISRE. Specifically, increased RNF6 expression in myeloid cells of patients with SLE correlated with high expression of ISGs. Our results uncover RNF6 as a positive mediator in the antiviral immune responses and suggest that RNF6 may contribute to predict interferon signaling in SLE.