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Genome Editing and Gene Therapies: Complex and Expensive Drugs
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Lentiviruses include primate retroviruses and non-primate retroviruses. A well-known example of a lentivirus (Retroviridae family), is the Human Immunodeficiency Virus (HIV). Retroviruses are capable of integrating significant amounts of viral cDNA into the DNA of the host cell; they can be inherited via integration of the viral into the host germline genome. Their ability to infect both dividing and non-dividing cells and a higher insert capacity compared with AAVs makes them well suited for efficient gene-therapy. The genes of lentiviruses such as pol encode enzymes as, e.g., reverse transcriptase (RT), integrase (IN) and protease, and structural proteins including Gp41 transmembrane envelope protein and Gp120 surface envelope protein, both encoded by the env gene, as well as P24 capsid protein, P17 matrix protein, and P9 capsid protein, all encoded by gag. The proteome also comprises regulatory genes and various assessor genes for regulation of viral gene expression, assembly and replication. Finally, two long terminal repeats (LTRs) contain sequences that are required for gene expression, reverse transcription and integration into the host chromosomes, together with the packaging ψ signal and the polypurine tract (PPT) involved in the initiation of plus-strand DNA synthesis by RT (conversion of the single-stranded RNA (ssRNA) genome into double-stranded DNA (dsDNA)) as a prerequisite of replication of retroviral RNA into double-stranded DNA provirus. IN catalyzes the integration of the proviral DNA into the host genome and protease is involved in virion maturation via gag-pol cleavage (Escors and Breckpot, 2010; Volkmann et al., 1993).
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Long terminal repeat (LTR) refers to a characteristic sequence of nucleotides that occurs at each end of a retrovirus element that has become integrated into the host genome. Involved in the integration process.
Inter-retrotransposon amplified polymorphism markers revealed long terminal repeat retrotransposon insertion polymorphism in flax cultivated on the experimental fields around Chernobyl
Published in Journal of Environmental Science and Health, Part A, 2020
Veronika Lancíková, Jana Žiarovská
Two major classes of TEs are known up to this date, I and II.[24] Class I of TEs represents retrotransposons, which transpose through reverse transcription of RNA and class II of TEs are DNA transposons which transposition do not involve RNA but cut-and-paste mechanism, and several transposase enzymes.[25] Retrotransposons are further divided into the LTR (Long Terminal Repeat) and non-LTR retrotransposon.[26] LTR-retrotransposons are classified into two major groups Copia and Gypsy consisting of many families which constitute from 40 to 70% of total genomic DNA.[27] Structural and functional characteristics of retrotransposons are similar to retroviruses but retrotransposons are not infectious in contrast to retroviruses.[28] Retrotransposons are largely quiescent during plant development and their activity in plant genomes is strictly controlled, although the transcription and transposition can be activated by different forms of abiotic and biotic stresses.[29,30] Retrotransposons as the most widespread class of TEs[31] are highly suitable for detection of genetic polymorphism. Molecular markers based on retrotransposon activity represent a pivotal techniques for analyses of genetic polymorphism and genomic changes in plants.[32] Various stress impulses, depending on stress factor and organism, may induce the specific response of LTR-retrotransposons activity. In photosynthetic eukaryotes, stress can activate the mechanism of retransposition termed „copy and paste”, thus reverse transcription and re-incorporation of retroelement into a new location in genome.[33] For instance, incorporation of activated LTR-retrotransposons within gene coding region may result in the inhibition of gene expression, furthermore the transcription activity of adjoining genes can be affected as well.[34,35]