A fluorescence-based reporter system to monitor human papillomavirus E2-dependent reporter activation in keratinocytes

Human papillomavirus (HPV) gene regulation is closely linked to epithelial biology, but simple experimental systems for visualizing functional viral transcriptional activity in keratinocytes remain limited. This study presents a fluorescence-based reporter system designed to monitor HPV E2-dependent reporter activation in HaCaT keratinocytes. Using an enhanced green fluorescent protein (GFP) reporter controlled by an E2-responsive promoter cassette, the system enables direct microscopic visualization and semiquantitative image-based analysis of reporter activation. Cotransfection with an HPV16 early-region plasmid increased normalized GFP signal compared with reporter-only controls, supporting the use of this platform as a reproducible proof-of-principle assay. The system is not intended as a diagnostic test or infectivity assay, but provides a technically simple experimental tool for studying HPV-related transcriptional regulation in vitro.