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A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription.Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobile genetic elements to proliferate within the host genome, and by eukaryotic cells to extend the telomeres at the ends of their linear chromosomes.
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. [2] After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backward).
These proteins are typically involved in the early stages of genome replication, and include reverse transcriptase and integrase. Reverse transcriptase is the virally encoded RNA-dependent DNA polymerase. The enzyme uses the viral RNA genome as a template for the synthesis of a complementary DNA copy. Reverse transcriptase possesses [RNase H ...
Upon infection and replication catalyzed by reverse transcriptase, recombination between the two genomes can occur. [81] [82] Recombination occurs as the single-strand, positive-sense RNA genomes are reverse transcribed to form DNA. During reverse transcription, the nascent DNA can switch multiple times between the two copies of the viral RNA.
Colourized transmission electron micrograph of SARS-CoV-2, the cause of the COVID-19 pandemic and a ribovirian. Animal viruses in Riboviria include orbiviruses, which cause various diseases in ruminants and horses, including Bluetongue virus, African horse sickness virus, Equine encephalosis virus, and epizootic hemorrhagic disease virus. [45]
In order to carry out their life cycle, the retrovirus relies heavily on the host cell's machinery. Protease degrades peptide bonds of the viral polyproteins, making the separate proteins functional. Reverse transcriptase functions to synthesize viral DNA from the viral RNA in the host cell's cytoplasm before it enters the nucleus.
However, the reverse transcriptase protein that often comes with the RNA virus can be used as an indirect target for RNA viruses, preventing transcription and synthesis of viral particles. [19] (This is the basis for anti-AIDs and anti-HIV drugs [20])
Through reverse transcription, retrotransposons amplify themselves quickly to become abundant in eukaryotic genomes such as maize (49–78%) [3] and humans (42%). [4] They are only present in eukaryotes but share features with retroviruses such as HIV, for example, discontinuous reverse transcriptase-mediated extrachromosomal recombination. [5] [6]