Epstein-Barr virus episome stability is coupled to a delay in replication timing

Area of Science:

• Virology
• Molecular Biology
• Epigenetics

Background:

• Temporal regulation of DNA replication is crucial for genome stability.
• Epstein-Barr virus (EBV) episomes are DNA molecules maintained extrachromosomally within host cells.

Purpose of the Study:

• To investigate the role of replication timing in EBV genome stability.
• To identify factors regulating EBV replication timing and their impact on episome stability.

Main Methods:

• Hydroxyurea (HU) treatment to alter EBV replication timing.
• Analysis of histone modifications (acetylation) and protein binding (TRF2) at the EBV origin of replication (OriP).
• Genetic manipulation (site-directed deletion, shRNA depletion) of TRF2 binding sites and HDAC inhibition.

Main Results:

• EBV replicates in mid- to late S phase; accelerated replication reduces genome stability.
• HU treatment advanced EBV replication, correlated with histone hyperacetylation and reduced TRF2 binding at OriP.
• TRF2 depletion or HDAC inhibition advanced EBV replication timing and decreased EBV genome copy number.

Conclusions:

• A complex of TRF2 and histone deacetylases (HDAC1/2) at OriP delays EBV replication initiation.
• This TRF2-HDAC complex acts as a checkpoint, promoting EBV episome stability.