HECTD3 promotes gastric cancer progression by mediating the polyubiquitination of c-MYC

The E3 ubiquitin ligase HECTD3 is homologous with the E6 related protein carboxyl terminus, which plays a vital role in biological modification, including immunoreactivity, drug resistance and apoptosis. Current research indicates that HECTD3 promotes the malignant proliferation of multiple tumors and increases drug tolerance. Our study primarily explored the important function and effects of HECTD3 in gastric cancer. Here, we discovered that HECTD3 is abnormally activated in gastric cancer, and the clinical prognosis database suggested that HECTD3 was strongly expressed in gastric cancer. Depletion of HECTD3 restrained the proliferative and clone abilities of cells and induced the apoptosis of gastric cancer cells. Mechanistically, our findings revealed that interaction between HECTD3 and c-MYC, and that the DOC domain of HECTD3 interacted with the CP and bHLHZ domains of c-MYC. Furthermore, we discovered that HECTD3 mediates K29-linked polyubiquitination of c-MYC. Then, our research indicated that cysteine mutation at amino acid 823 (ubiquitinase active site) of HECTD3 reduces the polyubiquitination of c-MYC. Our experimental results reveal that HECTD3 facilitates the malignant proliferation of gastric cancer by mediating K29 site-linked polyubiquitination of c-MYC. HECTD3 might become a curative marker.