reverse transcriptase

(noun)

An enzyme that catalyzes the formation of DNA from RNA; found in retroviruses.

Related Terms

Examples of reverse transcriptase in the following topics:

  • Nucleotide and Nonnucleotide Reverse Transcriptase Inhibitors

    • Reverse transcriptase in viruses is inhibited by nucleoside (nucleotide) analogues or drugs that change the conformation of the enzyme.
    • Reverse transcriptase is an enzyme that has the ability to transcribe single-stranded DNA from a single-stranded RNA chain.
    • Viruses that use reverse transcriptase to convert their genetic material (RNA) into DNA are called retroviruses.
    • Non-nucleotide reverse transcriptase inhibitors bind to a different site, not the active one, of the reverse transcriptase enzyme.
    • Non-nucleotide inhibitors are non-competitive inhibitorsof reverse transcriptase.

  • Retroviruses and Hepadnavirus

    • Hepadnaviruses, retroviruses, use virally encoded reverse transcriptase to convert RNA into DNA.
    • One defining feature is the use of reverse transcriptase to convert the positive-sense RNA into DNA.
    • Once in the host's cell, the RNA strands undergo reverse transcription in the cytoplasm and are integrated into the host's genome, at which point the retroviral DNA is referred to as a provirus.
    • One has a negative-sense orientation, and the other, shorter, strand has a positive-sense orientation.Hepadnaviruses replicate through an RNA intermediate (which they transcribe back into cDNA using reverse transcriptase).
    • The reverse transcriptase becomes covalently linked to a short 3- or 4-nucleotide primer.

  • Primer Extension Analysis

    • The primer is allowed to anneal to the RNA and reverse transcriptase is used to synthesize cDNA from the RNA until it reaches the 5' end of the RNA.
    • In one, the modified nucleotide cannot be recognized by the polymerase or reverse transcriptase; in such cases, the chain ends at the site of modification.

  • Retroviral RNA Genome

    • The retroviral genome contains the elements needed for reverse transcription and all other activities of a retrovirus.
    • Pol proteins, such as the reverse transcriptase (RT), are responsible for synthesis of viral DNA and integration into host DNA after infection.
    • Reverse transcription occurs in the cytoplasm of host cell.
    • In this process, viral ssRNA is transcribed by the viral reverse transcriptase (RT) into double stranded DNA.
    • Reverse transcription takes place in 5'→3' direction. tRNA ("cloverleaf") hybridizes to PBS and provides -OH group for initiation of reverse transcription. 1) Complementary DNA (cDNA) is formed. 2) Template in RNA:DNA hybrid is degraded by RNase H domain of reverse transcriptase 3) DNA:tRNA is transferred to the 3'-end of the template. 4) First strand synthesis takes place. 5) The rest of viral ssRNA is degraded by RNase H, except for the PP site. 6) Synthesis of second strand of ssDNA is initiated from the 3'-end of the template. tRNA is necessary to synthesis of complementary PBS 7) tRNA is degraded 8) PBS from the second strand hybridizes with the complementary PBS on the first strand. 9) Synthesis of both strands is completed by the DNA Polmerase function of reverse transcriptase.

  • Viral Identification

    • Reverse transcribing viruses: These have ssRNA (Retroviridae, Metaviridae, Pseudoviridae) or dsDNA (Caulimoviridae, and Hepadnaviridae) in their particles.
    • Reverse transcribing viruses with RNA genomes (retroviruses), use a DNA intermediate to replicate, whereas those with DNA genomes (pararetroviruses) use an RNA intermediate during genome replication.
    • Both types use a reverse transcriptase, or RNA-dependent DNA polymerase enzyme, to carry out the nucleic acid conversion.
    • Retroviruses integrate the DNA produced by reverse transcription into the host genome as a provirus as a part of the replication process.
    • They are susceptible to antiviral drugs that inhibit the reverse transcriptase enzyme, e.g. zidovudine and lamivudine.

  • HIV Attachment and Host Cell Entry

    • After HIV has bound to the target cell, the HIV RNA and various enzymes (including reverse transcriptase, integrase, ribonuclease, and protease) are injected into the cell.
    • Steps in the HIV Replication Cycle: Fusion of the HIV cell to the host cell surface.Cell Entry, HIV RNA, reverse transcriptase, integrase, and other viral proteins enter the host cell.Viral DNA is formed by reverse transcription.Viral DNA is transported across the nucleus and integrates into the host DNA.New viral RNA is used as genomic RNA to make viral proteins.New viral RNA and proteins move to cell surface and a new, immature, HIV virus forms.Virus maturation and protease release of individual HIV proteins.

  • Steps of Virus Infections

    • Retroviruses, such as HIV, have an RNA genome that must be reverse transcribed into DNA, which then is incorporated into the host cell genome.
    • To convert RNA into DNA, retroviruses must contain genes that encode the virus-specific enzyme reverse transcriptase, which transcribes an RNA template to DNA.
    • Reverse transcription never occurs in uninfected host cells; the needed enzyme, reverse transcriptase, is only derived from the expression of viral genes within the infected host cells.
    • These drugs, including the reverse transcriptase inhibitor AZT, inhibit HIV replication by reducing the activity of the enzyme without affecting the host's metabolism.

  • HIV and AIDS

    • Upon entry into the target cell, the viral RNA genome is converted (reverse transcribed) into double-stranded DNA by a virally encoded reverse transcriptase that is transported along with the viral genome in the virus particle.
    • Abacavir, a nucleoside analog reverse transcriptase inhibitor (NARTI or NRTI) is used to treat HIV.
    • Initially treatment is typically a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside analogue reverse transcriptase inhibitors(NRTIs).

  • Replicative Cycle of HIV

    • Shortly after the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the single-stranded (+)RNA genome from the attached viral proteins and copies it into a complementary DNA (cDNA) molecule.
    • The process of reverse transcription is extremely error-prone, and the resulting mutations may cause drug resistance or allow the virus to evade the body's immune system.
    • The reverse transcriptase also has ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA-dependent DNA polymerase activity that creates a sense DNA from the antisense cDNA.
    • Steps in the HIV Replication Cycle: Fusion of the HIV cell to the host cell surface.Cell Entry, HIV RNA, reverse transcriptase, integrase, and other viral proteins enter the host cell.Viral DNA is formed by reverse transcription.Viral DNA is transported across the nucleus and integrates into the host DNA.New viral RNA is used as genomic RNA to make viral proteins.New viral RNA and proteins move to cell surface and a new, immature, HIV virus forms.Virus maturation and protease release of individual HIV proteins.

  • Double-Stranded RNA Viruses: Retroviruses

    • Retroviruses are viruses that are able to reverse transcribe their RNA genome into DNA, which is then integrated into a host genome.
    • A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome.
    • Once in the host's cell, the RNA strands undergo reverse transcription in the cytoplasm and are integrated into the host's genome, at which point the retroviral DNA is referred to as a provirus.
    • Their RNA is reverse-transcribed into DNA, which is integrated into the host cell's genome (when it becomes a provirus), and then undergoes the usual transcription and translation processes to express the genes carried by the virus .