Provirus

Provirus - the genome of a virus embedded in the DNA of a host cell. The process of incorporating a provirus into the genome is called integration; this reaction is catalyzed by the enzyme integrase .

Provirus is a stage in the life cycle of retroviruses . When retroviruses enter the host cell, the genomic RNA of the retrovirus is back transcribed into the DNA by the reverse transcriptase enzyme and inserted into the host genome by the integrase enzyme.

In the provirus stage, passive replication of viral DNA occurs along with the host DNA, with the provirus being transmitted to all descendants of the infected cell. The integration of viral DNA into the host genome can occur both in latent infection and in productive infection. In the case of a productive infection, the provirus is actively transcribed into mRNA , which directly encodes viral proteins, which leads to infection of new cells. With latent infection, the provirus is transcriptionally suppressed.

Latent infection can go into the productive phase in the event of a change in environmental conditions, when the immune status of the host changes, and the transcription of the virus genome is activated. As a result of viral gene expression and viral protein synthesis, the host cell dies.

According to some reports, proviral nucleotide sequences from endogenous retroviruses make up 8% of the human genome ^[1] .

Human immunodeficiency virus and human T-lymphotropic virus have a provirus stage in the life cycle.

An adeno-associated virus that is not a retrovirus can also integrate into the host chromosomes .