ZPR1 Is Dispensable for HPV R-Loop Resolution but Regulates Host R-Loop Dynamics

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• R-loops, DNA-RNA hybrids, form during papillomavirus transcription and are critical for HPV episomal maintenance.
• ZPR1 protein recruits SETX helicase to resolve R-loops in mammalian cells.
• The role of ZPR1 and E2 in HPV R-loop resolution is not fully understood.

Purpose of the Study:

• To investigate the role of ZPR1 and E2 in HPV R-loop resolution and maintenance.
• To determine the impact of ZPR1 depletion on viral and cellular R-loops.
• To analyze the expression of ZPR1 and SETX in HPV-associated cancers.

Main Methods:

• Depletion of ZPR1 using siRNA.
• Analysis of R-loop formation using molecular assays.
• Co-immunoprecipitation to detect protein complexes.
• TCGA dataset analysis for gene expression.

Main Results:

• ZPR1 depletion reduced viral R-loops but increased cellular R-loops, suggesting it's not required for HPV R-loop resolution.
• E2 protein was found associated with R-loops, and its overexpression enhanced R-loop formation.
• ZPR1, but not SETX, mRNA levels were significantly reduced in HPV-positive cervical and head and neck cancers.
• E2 may promote R-loop accumulation by sequestering SETX.

Conclusions:

• ZPR1 is not essential for HPV R-loop resolution, unlike in other mammalian systems.
• HPV E2 protein plays a dual role in R-loop dynamics, mediating resolution while promoting accumulation in the host genome.
• Altered ZPR1 expression in HPV-positive cancers suggests a potential role in tumorigenesis.