WDR76 is a RAS binding protein that functions as a tumor suppressor via RAS degradation

Abstract

Stability regulation of RAS that can affect its activity, in addition to the oncogenic mutations, occurs in human cancer. However, the mechanisms for stability regulation of RAS involved in their activity and its roles in tumorigenesis are poorly explored. Here, we identify WD40-repeat protein 76 (WDR76) as one of the HRAS binding proteins using proteomic analyses of hepatocellular carcinomas (HCC) tissue. WDR76 plays a role as an E3 linker protein and mediates the polyubiquitination-dependent degradation of RAS. WDR76-mediated RAS destabilization results in the inhibition of proliferation, transformation, and invasion of liver cancer cells. WDR76−/− mice are more susceptible to diethylnitrosamine-induced liver carcinogenesis. Liver-specific WDR76 induction destabilizes Ras and markedly reduces tumorigenesis in HRasG12V mouse livers. The clinical relevance of RAS regulation by WDR76 is indicated by the inverse correlation of their expressions in HCC tissues. Our study demonstrates that WDR76 functions as a tumor suppressor via RAS degradation.

Biochemical Reduction of the Topology of the Diverse WDR76 Protein Interactome

“…In addition, the prognostic summary in the Pathology Atlas for WDR76 in The Human Protein Atlas (Uhlen et al, 2017) lists WDR76 as an unfavorable prognostic marker in renal cancer, lung cancer, pancreatic cancer, and liver cancer. These links to cancer are supported by recent evidence of the role of WDR76 in regulating the RAS oncogene (Jeong et al, 2019).…”

“…WDR76 has been linked to the CUL4-DDB1 ubiquitin ligase complex in mammals where WDR76 is involved in regulating circadian rhythms (Tamayo et al, 2015). In addition, recently Jeong et al have shown that the CUL4-DDB1-WDR76 ubiquitin ligase complex is vital for the regulation of RAS levels via a polyubiquitination-dependent degradation mechanism required for inhibition of proliferation, transformation, and invasion in liver cancer cells (Jeong et al, 2019). Collectively, these studies support the idea that WDR76 may be an ubiquitin ligase E3 linker protein.…”

WDR76 degrades RAS and suppresses cancer stem cell activation in colorectal cancer

“…For viral production, HEK293T cells were transfected with pLVX-GFP-Control, pLVX-GFP-WDR76, pLVX-GFP-WDR76ΔNLS, pLKO.1-shControl-GFP, or pLKO.1-shWDR76-GFP, [19] together with the viral packaging psPAX2 and viral envelope pMD2G plasmids at a 2:2:1 ratio. Then, D-WT and D-MT cells were transduced with each lentivirus.…”

“…WDR76 (WD Repeat protein 76) is an E3 ligase that suppresses tumorigenesis of human hepatocellular carcinoma (HCC) cells by destabilizing RAS [19]. WDR76 has been identified as one of the proteins that interacts with H-RAS in human HCC tissues and destabilizes all three major RAS isoforms, H-RAS, K-RAS and N-RAS [19].…”

“…WDR76 (WD Repeat protein 76) is an E3 ligase that suppresses tumorigenesis of human hepatocellular carcinoma (HCC) cells by destabilizing RAS [19]. WDR76 has been identified as one of the proteins that interacts with H-RAS in human HCC tissues and destabilizes all three major RAS isoforms, H-RAS, K-RAS and N-RAS [19]. Here, based on our observation of increased RAS protein levels in CSC-like population with high expression of CSC markers compared to low CSC counterpart sorted from a human CRC cell line, we investigated the role of WDR76 as a modulator of RAS abundance and CSC activation contributing to tumorigenesis in CRC.…”