Nucleosome DNA unwrapping does not affect prototype foamy virus integration efficiency or site selection

Area of Science:

• Molecular Biology
• Virology
• Epigenetics

Background:

• Eukaryotic DNA is packaged into chromatin, requiring proteins to access DNA within this structure.
• Retroviral integrases (IN) must interact with chromatin to integrate viral cDNA during infection.

Purpose of the Study:

• To investigate the role of nucleosome DNA unwrapping in the retroviral integrase (IN) search for target DNA sites.
• To determine if increased nucleosome unwrapping affects PFV intasome-mediated integration.

Main Methods:

• Utilized purified prototype foamy virus (PFV) intasomes, comprising PFV IN tetramers and viral cDNA mimics.
• Generated modified nucleosomes using recombinant human histones with mutations (H3(K56Q), H4(K77ac, K79ac)) to increase DNA unwrapping rates.
• Assessed the impact of enhanced nucleosome unwrapping on PFV intasome integration activity.

Main Results:

• Increased nucleosome unwrapping rates, induced by histone modifications, did not affect PFV intasome-mediated integration.
• This contrasts with other DNA-binding proteins like transcription factors and DNA damage sensors that may utilize transient unwrapping.

Conclusions:

• PFV intasomes do not appear to utilize nucleosome DNA unwrapping as a mechanism for searching for target integration sites.
• This suggests a distinct DNA target search strategy for PFV integrase compared to other chromatin-interacting proteins.