HIV Reverse Transcriptase Synthesizes the DNA Copy
Reverse transcriptase is the enzyme responsible for synthesizing the DNA copy of HIV once it enters target cells. This enzyme is encoded by the HIV genome and is essential for converting the single-stranded viral RNA into double-stranded DNA that can integrate into the host cell's chromosomes 1, 2.
Mechanism of Action
Reverse transcriptase performs RNA-dependent DNA synthesis to convert the single-stranded HIV RNA genome into DNA, a process unique to retroviruses 1, 2.
The enzyme is packaged within HIV virion particles and enters the host cell along with the viral RNA genome 1.
HIV-1 reverse transcriptase consists of two subunits: a 66 kDa (p66) subunit and a 51 kDa (p51) subunit, forming a heterodimer that is critical for enzymatic activity 2.
The enzyme has multifunctional capabilities, including both DNA polymerase activity and ribonuclease H (RNase H) activity, which work together to complete the reverse transcription process 3, 4.
Clinical Significance
Reverse transcriptase is the primary target of major antiretroviral drugs used in HIV treatment, including nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) 5.
The enzyme lacks proofreading function, leading to frequent mutations and the emergence of drug-resistant viral strains 5, 2.
Baseline reverse transcriptase genotype testing is recommended before initiating antiretroviral therapy due to high rates of transmitted drug resistance 5.
Why Not the Other Options
- Protons are subatomic particles with no enzymatic function
- Ribosomes synthesize proteins from mRNA but do not synthesize DNA
- Integrase is a different HIV enzyme that inserts the newly synthesized viral DNA into the host chromosome, but does not create the DNA copy itself 5