Interaction between Human Papillomavirus-Encoded E6 Protein and AurB Induces Cell Immortalization and Proliferation—A Potential Target of Intervention

SIMPLE SUMMARY: This study identified that Aurora kinase B (AurB), a cellular protein that is upregulated in human cancers, is a bona fide interacting partner of HPVE6. HPVE6 complexes with AurB at the C-terminus end of E6, upstream of the E6-PBM. The AurB-E6 complex forms predominantly in the nucleus or mitotic cells. The positive correlation between E6 and AurB protein in HPV-positive cancer cells confers an increased cell proliferation and growth, and the eventual tumour formation. This study also underlined that the AurB-E6 complex could be a therapeutic target. However, the commercially available Aurora kinase inhibitors to date might not be selective toward HPV-positive cancer cells. Hence, this lack should be addressed. ABSTRACT: The human papillomavirus E6 and E7 oncoproteins interact with a different subset of host proteins, leading to dysregulation of the apoptotic, cell cycle, and signaling pathways. In this study, we identified, for the first time, that Aurora kinase B (AurB) is a bona fide interacting partner of E6. We systematically characterized the AurB-E6 complex formation and its consequences in carcinogenesis using a series of in vitro and cell-based assays. We also assessed the efficacy of Aurora kinase inhibitors in halting HPV-mediated carcinogenesis using in vitro and in vivo models. We showed that AurB activity was elevated in HPV-positive cells, and this correlated positively with the E6 protein level. E6 interacted directly with AurB in the nucleus or mitotic cells. A previously unidentified region of E6, located upstream of C-terminal E6-PBM, was important for AurB-E6 complex formation. AurB-E6 complex led to reduced AurB kinase activity. However, the AurB-E6 complex increased the hTERT protein level and its telomerase activity. On the other hand, AurB inhibition led to the inhibition of telomerase activity, cell proliferation, and tumor formation, even though this may occur in an HPV-independent manner. In summary, this study dissected the molecular mechanism of how E6 recruits AurB to induce cell immortalization and proliferation, leading to the eventual cancer development. Our findings revealed that the treatment of AZD1152 exerted a non-specific anti-tumor effect. Hence, a continuous effort to seek a specific and selective inhibitor that can halt HPV-mediated carcinogenesis should be warranted.