From the Guidelines
The mechanism of action of reverse transcriptase involves the conversion of viral RNA into viral DNA, a process known as reverse transcription.
Key Steps in Reverse Transcription
- Reverse transcriptase catalyzes the synthesis of a complementary DNA (cDNA) copy from the viral RNA template, which is then elongated to form a double-stranded DNA molecule 1.
- This process is a critical step in the replication cycle of retroviruses, such as HIV.
Role in Viral Replication
- The double-stranded DNA virus inserts into the cell genome, using information carried in the 5' and 3' long terminal repeats 1.
- Reverse transcriptase is carried by the virus and converts RNA to DNA, allowing the virus to integrate into the host cell's genome.
Inhibition of Reverse Transcriptase
- Antiretroviral medications like zidovudine, lamivudine, and tenofovir inhibit reverse transcriptase activity and prevent viral DNA elongation 1.
- These medications are crucial in the treatment of HIV and other retroviral infections, highlighting the importance of understanding the mechanism of action of reverse transcriptase.
From the FDA Drug Label
The principal mode of action of ZDV-TP is inhibition of reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue The principal mode of action of 3TC-TP is inhibition of HIV-1 reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue
The mechanism of action of reverse transcriptase in viral replication is inhibition of reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue. This is the mechanism by which zidovudine and lamivudine, both nucleoside analogues, exert their antiviral effects against HIV-1.
- Key points:
- Reverse transcriptase is an enzyme that plays a crucial role in the replication of retroviruses, including HIV-1.
- Zidovudine and lamivudine are phosphorylated to their active triphosphate metabolites, which are then incorporated into the viral DNA, causing chain termination and inhibiting viral replication.
- This mechanism of action is specific to reverse transcriptase and does not affect cellular DNA polymerases to a significant extent. 2 3
From the Research
Mechanism of Action of Reverse Transcriptase
The mechanism of action of reverse transcriptase in viral replication involves the conversion of single-stranded RNA into double-stranded DNA through the enzyme's DNA polymerase and ribonuclease H activities 4, 5. This process is critical for the replication of retroviruses and related retrotransposons.
Key Steps in Reverse Transcription
- Initiation of minus-strand DNA synthesis occurs by extension of a tRNA primer associated with the viral genome 6.
- Plus-strand DNA synthesis is initiated from an RNase H-resistant polypurine tract of the genomic RNA that remains bound to the newly synthesized minus-strand DNA 6.
- The coordinated action of both enzymatic activities converts single-stranded RNA into a double-stranded DNA that is flanked by identical sequences known as long terminal repeats (LTRs) 4.
Enzymatic Activities of Reverse Transcriptase
- DNA polymerase activity: synthesizes DNA using RNA or DNA as templates 4, 5.
- Ribonuclease H activity: degrades RNA when forming RNA/DNA hybrids 4, 5.
- Lack of proofreading activity: results in high intrinsic error rates 4.
- High recombination rates: promoted by poor processivity that causes template switching, a hallmark of reverse transcription 4, 7.
Inhibition of Reverse Transcriptase
- HIV-1 RT inhibitors acting on its polymerase activity constitute the backbone of current antiretroviral therapies 4.
- Novel drugs, including ribonuclease H inhibitors, are still necessary to fight HIV infections 4.
- Triple-helix forming oligonucleotides with viral RNA can inhibit reverse transcription by preventing RNase H cleavage of the PPT-RNA.DNA hybrid and initiation of plus-strand DNA synthesis 8.