Reverse transcription

The virus of some, I have the ability to transcribe RNA (for example, due to HIV, AIDS), to DNA. You have the HIV RNA genome is replicated in DNA. DNA thus obtained may be fused to the genomic DNA of the host cell. Major enzyme involved in the synthesis of RNA from DNA are called reverse transcriptase. In the case of HIV, reverse transcriptase is responsible for synthesis of a complementary strand of the DNA of the virus genome RNA and (cDNA). It is an enzyme ribonuclease H, in order to form a double helix structure of DNA (“on cDNA”), reverse transcriptase and RNA synthesize a complementary strand of DNA next. It was integrated into the genome of the host cell integrase enzyme that causes a host cell in order to repeat the cDNA of decomposing to produce viral proteins incorporated into new virus particles. In HIV, as a result, the host cells undergo apoptosis or programmed cell death of T cells. However, in other retroviruses, as the virus buds from the cell, the host cell, has been left as it is.

Reverse transcription

In eukaryotic cells, specific, and includes an enzyme having reverse transcriptase activity called telomerase. Telomerase is a reverse transcriptase which extends the ends of linear chromosomes. The synthesized “junk” DNA or DNA sequences that are repeated, telomerase RNA carry therefrom. This iterative sequence can be called a telomere DNA, is considered as a “cap” on chromosomes. Linear chromosomes since the duplicated each time, which is important, it is shortened. Not a repeat sequence is not essential for DNA sequence encoding a protein located at the ends of chromosomes, some of them, but ends of chromosomes, “hat” or “junk” DNA, the shortening is eliminated.

Often, without losing the DNA sequence cancer cells encode proteins important in order to be able to replicate their genome indefinitely, Telomerase is activated in cancer cells. Activation of telomerase may be part of a process that allows cancer cells become immortal. By using the remaining 10% of the alternate route is known as the alternate telomere elongation and maintenance ALT telomere, telomerase in recycling factor cancers indicates that occur in 90% of the carcinogenic all tumors in vivo by telomere elongation Because it is.

Found separated by Howard Temin at the University of Wisconsin-Madison in virion RSV, in David Baltimore independently, reverse transcriptase, was a 2 RNA tumor viruses at MIT in 1970 and R-MLV again RSV. So inconsistent with the central dogma of molecular biology said is transcribed into RNA, which is translated into protein DNA, the idea of ​​reverse transcription, it is very unpopular at first. However, in 1970, David Baltimore scientists and Howard Temin When is the possibility that the reverse transcription of both names independent reverse transcriptase, genetic information is allowed finally to be sent in this way I have found an enzyme involved. It is encoded by the viral reverse transcription using the enzymatic replication process, enzymes are used. Then, to use their genome the enzyme reverse transcriptase RNA in a DNA that is integrated into the host genome is replicated therewith, for example, reverse transcription of RNA viruses such as retroviruses. The reverse transcription, a DNA virus, such as hepadnaviruses such as, RNA can be used as a template for the assembly, and you can make the DNA strand. HIV-infected persons using this enzyme. It would not have been able to cause the failure to reproduce the Zu reverse transcription viral genome is incorporated into the host cell.

To create a double-stranded DNA and the transfer direction of transcription of the DNA product short initial RNA-dependent DNA synthesis to the acceptor template region at the other end of the genome that can be processed to reach by reverse transcriptase later The DNA-dependent DNA activity contains.  It is located at the 5 ‘end 3’ end of the retroviral RNA. Place called (PBS) primer binding sites are annealed primers viral RNA is called the leader of PBS FIG 5 ‘is referred to the end of RNA 3 end of the RNA to a site and, as a PBS U5’ have. It is developed with the double-stranded viral RNA primer tRNA is paired with form-based and PBS 22 and 14 nucleotides. Fact ‘reverse transcription Since DNA was synthesized from 3 that is located near the 5 PBS end of the primer in’ to 3 ‘(for RNA) 5 direction, by the end of the viral RNA, a rarity There is no ‘. Therefore, the position, the reverse transcriptase primer and achieves comprising (RN RNase H), and various enzymes DNA polymerase and several steps, ribonuclease H. Go to the 3 ‘end of the viral RNA, and it is required to develop a polynucleotide.  Reverse transcriptase of HIV have ribonuclease activity that degrades the viral RNA during the synthesis of DNA-dependent DNA polymerase and copy DNA with the sense DNA strand antisense DNA to form an intermediate double-stranded DNA virus (vDNA).

If you want to play in the life cycle of a retrovirus, and there are three different systems of the next. First, the present invention, reverse transcriptase to synthesize a complementary strand viral DNA and viral RNA, the DNA subsequently. The DNA polymerase of the host cell, when duplicating an integrated viral DNA, replication process of the second occurs. Finally, I can transcription of RNA polymerase II proviral DNA in RNA is packaged in virions. As a result, the mutation can occur in one or all duplicate one of these steps. Since then, that unlike the DNA polymerase of all the other does not have a high error rate on record at the time of the RNA correction capability, to DNA by reverse transcriptase. This high error rate can accumulate rapidly as compared with that mutation to examine the morphology of replication. In reverse transcriptase generation of commercially available, has been cited by the leadership as an error rate of up to 1 M-MLV 30,000 for base and base of 17,000 AMV from 1 by Promega. Also produce non-enzyme reverse transcription single nucleotide polymorphism, for example, to be involved in processes such as creating meaningless transcripts artificial transcription united and exon shuffling is shown. This reverse transcriptase that can be fully demonstrated in vivo, the switching operation of the template to be one reason for the discovery of transcripts without thousands annotate the genome of the model organism has been speculated was.