Features of the genome: infectious viruses have 3 main genes coding for the viral proteins in the order: 5´-gag-pol-env-3´.
There are additional genes (also called accessory genes) depending on the virus (e.g., for HIV-1: vif, vpr, vpu, tat, rev, nef) whose products are involved in regulation of synthesis and processing viral RNA and other replicative functions.
The Long terminal repeat (LTR) is about 600nt long, of which the U3 region is 450, the R sequence 100 and the U5 region some 70 nt long.
Viral proteins involved in early stages of replication include Reverse Transcriptase and Integrase. Reverse Transcriptase (RT) 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. RT also has RNaseH activity for destruction of the RNA-template.
Integrase (IN) binds both the viral cDNA generated by RT and the host DNA. Processing of the LTR by IN is performed prior to insertion of the viral genome into the host DNA.
Although transmission is generally via infectious particles, lentiviruses are capable of infecting neighboring cells in direct contact with the host cells, without having to form extracellular particles.
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