Chromosomal integration of LTR-flanked DNA in yeast expressing HIV-1 integrase: down regulation by RAD51

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• HIV-1 integrase (IN) is crucial for viral DNA integration.
• The sufficiency of IN for in vivo integration and its interaction with host cell machinery are not fully understood.

Purpose of the Study:

• To establish a yeast cellular integration system to study HIV-1 IN in isolation.
• To identify cellular factors involved in the integration process and their interaction with IN.

Main Methods:

• Expression of HIV-1 integrase as the sole viral protein in yeast.
• Targeting integrase to yeast chromosomes for integration studies.
• Investigating interactions between HIV-1 IN and yeast proteins, specifically RAD51.

Main Results:

• HIV-1 integrase is necessary and sufficient for integrating DNA with viral LTRs into the yeast genome.
• Physical interaction between HIV-1 IN and yeast RAD51 protein was demonstrated.
• RAD51 protein inhibited HIV-1 integrase activity both in vitro and in vivo.

Conclusions:

• The yeast system allows independent study of the HIV-1 integration step.
• RAD51 acts as a novel cofactor for HIV-1 integrase, downregulating its activity.
• RAD51 may function as a cellular restriction factor against HIV infection.