The R2TP complex stabilises E7 to drive human papillomavirus-mediated pathogenesis in cellular models of cervical cancer

Abstract

Human papillomaviruses (HPVs), particularly types 16 and 18, are major contributors to cervical cancer through the oncogenic activities of the E6 and E7 proteins. These viral proteins inactivate the tumour suppressors p53 and pRB, driving uncontrolled cellular proliferation. In this study, we investigated the interaction between the HPV E7 protein and the R2TP complex, a co-chaperone involved in essential cellular functions, including ribosome biogenesis, transcription, and macromolecular assembly. We identified PIH1D1, a core R2TP subunit, as an interacting partner of HPV16 and HPV18 E7 proteins. Mutagenesis and pull-down assays showed that phosphorylation of HPV E7 by casein kinase 2 (CK2) is critical for this interaction, as mutations of serine residues within the CK2 phospho-acceptor site on E7 disrupted the binding with PIH1D1. Furthermore, PIH1D1 facilitated the association of E7 with the retinoblastoma protein (pRB), forming a complex that likely promotes cancer cell proliferation. Immunohistochemical analysis of cervical cancer tissues revealed overexpression of PIH1D1, RUVBL1, and RPAP3—key components of the R2TP complex. Functional assays confirmed that PIH1D1 is crucial for cervical cancer cell growth and migration, as its silencing reduced E7 stability and impaired proliferation. Collectively, these findings highlight that PIH1D1, and by extension, the R2TP complex, is integral to the HPV-driven malignancy and suggest potential as therapeutic targets in HPV-related cancers. Importance Despite being largely preventable through vaccination, cervical cancer is a significant concern for public health. Research is essential to understand the factors contributing to its high incidence and mortality and to devise effective prevention and treatment strategies. We investigated the functional role of PIH1D1, a core subunit of the R2TP complex, in the HPV-mediated cervical carcinogenesis. The interaction of the R2TP complex, HPV E7, and the tumour suppressor pRB proteins may be essential in driving malignant transformation.