p53-dependent R-loop formation and HPV pathogenesis

Area of Science:

• Molecular Biology
• Genetics
• Oncology

Background:

• R-loops (RNA:DNA hybrids) regulate transcription but aberrant formation causes genomic instability.
• High-risk human papillomaviruses (HPV) are linked to cancers and increased DNA breaks.

Purpose of the Study:

• To investigate the role of R-loops in HPV pathogenesis.
• To determine the mechanism by which HPV induces R-loop accumulation.
• To explore R-loops as a therapeutic target in HPV-driven cancers.

Main Methods:

• Quantification of R-loop levels in HPV-positive and normal cells.
• Analysis of RNase H1's role in R-loop resolution.
• Investigating the impact of R-loop modulation on viral replication and DNA repair pathways.
• Assessing the role of the HPV E6 oncoprotein and p53 pathway.

Main Results:

• R-loop levels were up to 50-fold higher in HPV-positive cells and cervical carcinomas.
• RNase H1 depletion exacerbated R-loops, impairing viral functions and DNA repair gene expression.
• RNase H1 overexpression reduced R-loops and DNA breaks but blocked viral replication.
• HPV E6 oncoprotein induced R-loops by inhibiting p53 transcriptional activity.

Conclusions:

• Elevated R-loop levels are essential for the HPV life cycle and pathogenesis.
• HPV maintains high R-loop levels by suppressing the p53 pathway.
• Targeting R-loop resolution may offer a therapeutic strategy against HPV-driven cancers.