The membrane-associated ubiquitin ligase MARCHF8 stabilizes the human papillomavirus oncoprotein E7 by degrading CUL1 and UBE2L3 in head and neck cancer.

Since HPV oncoprotein E7 is essential for virus replication, HPV has to maintain high levels of E7 expression in HPV-infected cells. However, HPV E7 can be efficiently ubiquitinated by a ubiquitin ligase and degraded by proteasomes in the host cell. Mechanistically, the components of the E3 ubiquitin ligase complex CUL1 and UBE2L3 play an essential role in E7 ubiquitination and degradation. Here, we show that the membrane ubiquitin ligase MARCHF8 induced by HPV E6 stabilizes the E7 protein by degrading CUL1 and UBE2L3 and blocking E7 degradation through proteasomes. MARCHF8 knockout restores CUL1 and UBE2L3 expression, decreasing E7 protein levels and inhibiting the proliferation of HPV-positive cancer cells. Additionally, overexpression of CUL1 or UBE2L3 decreases E7 protein levels and suppresses in vivo tumor growth. Our results suggest that HPV maintains high E7 protein levels in the host cell by inducing MARCHF8, which may be critical for cell proliferation and tumorigenesis.