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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).
The Pol gene produces three proteins: a protease (PR), a reverse transcriptase endowed with an RT (reverse-transcriptase) and an RNAse H domains, and an integrase (IN). [8] Typically, LTR-retrotransposon mRNAs are produced by the host RNA pol II acting on a promoter located in their 5' LTR. The Gag and Pol genes are encoded in the same mRNA.
Although similar to the gene carrying out the same function in retroviruses, the env gene is used to determine whether the gene is retroviral or retrotransposon. If the gene is retroviral it can evolve from a retrotransposon into a retrovirus. They differ by the order of sequences in pol genes.
A protease is any enzyme that cuts proteins into segments. HIV's gag and pol genes do not produce their proteins in their final form, but as larger combination proteins; the specific protease used by HIV cleaves these into separate functional units.
For example, the gene CYP19 codes for aromatase P450, an important enzyme for estrogen synthesis, that is normally expressed in the brain and reproductive organs of most mammals. [18] However, in primates, an LTR-promoted transcriptional variant confers expression to the placenta and is responsible for controlling estrogen levels during ...
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, COVID-19, 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 long terminal repeat (LTR) is a pair of identical sequences of DNA, several hundred base pairs long, which occur in eukaryotic genomes on either end of a series of genes or pseudogenes that form a retrotransposon or an endogenous retrovirus or a retroviral provirus. All retroviral genomes are flanked by LTRs, while there are some ...
Env is a viral gene that encodes the protein forming the viral envelope. [1] The expression of the env gene enables retroviruses to target and attach to specific cell types, and to infiltrate the target cell membrane. [2] Analysis of the structure and sequence of several different env genes suggests that Env proteins are type 1 fusion machines. [3]