Targeting the Two Oncogenic Functional Sites of the HPV E6 Oncoprotein with a High‐Affinity Bivalent Ligand

Abstract

AbstractThe E6 oncoproteins of high‐risk mucosal (hrm) human papillomaviruses (HPVs) contain a pocket that captures LxxLL motifs and a C‐terminal motif that recruits PDZ domains, with both functions being crucial for HPV‐induced oncogenesis. A chimeric protein was built by fusing a PDZ domain and an LxxLL motif, both known to bind E6. NMR spectroscopy, calorimetry and a mammalian protein complementation assay converged to show that the resulting PDZ‐LxxLL chimera is a bivalent nanomolar ligand of E6, while its separated PDZ and LxxLL components are only micromolar binders. The chimera binds to all of the hrm‐HPV E6 proteins tested but not to low‐risk mucosal or cutaneous HPV E6. Adenovirus‐mediated expression of the chimera specifically induces the death of HPV‐positive cells, concomitant with increased levels of the tumour suppressor P53, its transcriptional target p21, and the apoptosis marker cleaved caspase 3. The bifunctional PDZ‐LxxLL chimera opens new perspectives for the diagnosis and treatment of HPV‐induced cancers.