Anti-RNF7 monoclonal antibody

Sensitive to apoptosis gene (SAG), also known as RBX2, ROC2, or RNF7, is a RING component of SCF E3 ubiquitin ligases, which regulates cellular functions through ubiquitylation and degradation of many protein substrates. Although our previous studies showed that SAG is transcriptionally induced by redox, mitogen and hypoxia via AP-1 and HIF-1, it is completely unknown whether and how SAG is ubiquitylated and degraded. Here we report that NEDD4-1, a HECT domain-containing E3 ubiquitin ligase, binds via its HECT domain directly with SAG's C-terminal RING domain and ubiquitylates SAG for proteasome-mediated degradation. Consistently, SAG protein half-life is shortened or extended by NEDD4-1 overexpression or silencing, respectively. We also found that SAG bridges NEDD4-1 via its C-terminus and CUL-5 via its N-terminus to form a NEDD4-1/SAG/CUL-5 tri-complex. Biologically, NEDD4-1 overexpression sensitizes cancer cells to etoposide-induced apoptosis by reducing SAG levels through targeted degradation. Thus, SAG is added to a growing list of NEDD4-1 substrates and mediates its biological function.

BACKGROUND & AIMS: Polymorphisms in IL28B were shown to affect clearance of hepatitis C virus (HCV) infection in genome-wide association (GWA) studies. Only a fraction of patients with chronic HCV infection develop liver fibrosis, a process that might also be affected by genetic factors. We performed a 2-stage GWA study of liver fibrosis progression related to HCV infection. METHODS: We studied well-characterized HCV-infected patients of European descent who underwent liver biopsies before treatment. We defined various liver fibrosis phenotypes on the basis of METAVIR scores, with and without taking the duration of HCV infection into account. Our GWA analyses were conducted on a filtered primary cohort of 1161 patients using 780,650 single nucleotide polymorphisms (SNPs). We genotyped 96 SNPs with P values <5 x 10(-5) from an independent replication cohort of 962 patients. We then assessed the most interesting replicated SNPs using DNA samples collected from 219 patients who participated in separate GWA studies of HCV clearance. RESULTS: In the combined cohort of 2342 HCV-infected patients, the SNPs rs16851720 (in the total sample) and rs4374383 (in patients who received blood transfusions) were associated with fibrosis progression (P-combined = 8.9 x 10(-9) and 1.1 x 10(-9), respectively). The SNP rs16851720 is located within RNF7, which encodes an antioxidant that protects against apoptosis. The SNP rs4374383, together with another replicated SNP, rs9380516 (P-combined = 5.4 x 10(-7)), were linked to the functionally related genes MERTK and TULP1, which encode factors involved in phagocytosis of apoptotic cells by macrophages. CONCLUSIONS: Our GWA study identified several susceptibility loci for HCV-induced liver fibrosis; these were linked to genes that regulate apoptosis. Apoptotic control might therefore be involved in liver fibrosis.