The enzyme HIV uses to integrate its DNA into the host genome is integrase. Integration is a defining step in the retroviral life cycle: once inserted, the viral DNA becomes a provirus within a host chromosome and can be copied whenever the cell divides or transcribed to make new viral components.
HIV begins with an RNA genome, so reverse transcriptase first makes a DNA copy inside the infected cell. Integrase then binds the ends of that viral DNA, performs 3′ processing, and catalyzes strand transfer into host DNA. Host-cell repair enzymes finish sealing the integration site. Integrase works with viral DNA and host factors, including LEDGF/p75, which helps guide the integration complex toward suitable chromatin regions.
The enzymes in the options have different jobs. Reverse transcriptase makes DNA from the RNA genome; protease cuts long viral polyproteins into functional proteins; DNA polymerase is not the enzyme that performs HIV integration.
Because integration helps HIV persist in cells, integrase became an important drug target. Raltegravir, the first approved HIV integrase inhibitor, received U.S. approval in 2007.