Reverse transcriptase is an RNA-directed DNA polymerase common in retroviruses. The HIV retrovirus that causes AIDS contains a reverse transcriptase. Like other RNA-dependent polymerases, reverse transcriptase is very error prone because it contains no proofreading activity. The replication scheme of retroviral RNA is as follows:
1. Viral RNA in the host cell base pairs with a specific tRNA molecule to provide a primer for DNA replication.
2. Reverse transcriptase makes DNA towards the 5' end of the viral RNA.
3. RNase H partially degrades RNA from the RNA-DNA duplex, removing the 5' terminus.
4. The 3' terminus of the viral RNA base pairs with the overhanging DNA strand, forming a circle-like structure.
5. Reverse transcriptase makes a DNA copy of the entire genome, using the 3' end of the DNA strand as a primer.
6. The RNA strand of the duplex is removed and a DNA strand complementary to the first DNA strand is synthesized to form a duplex.
7. The duplex integrates into the host chromosome
The drug, 3'-Azido-2'3'-dideoxythymidine (AZT), when converted to the corresponding 5' triphosphate in cells, is an inhibitor of the HIV reverse transcriptase enzyme. Other nucleoside analogs, such as 2'3'-dideoxycytidine (ddC), 2'3'-dideoxyinosine (ddI), and 2'3'-didehydro-3'-deoxythymidine (d4T) (see here) are also converted to triphosphates and act by blocking DNA chain elongation after they are incorporated into DNA.
2. HIV Insite
3. General Replication Strategies for RNA Viruses