Proviruksen

Provirus is the form of a virus in which its genome is integrated into the DNA of a host cell. For many viruses, notably retroviruses such as HIV, the viral RNA genome is reverse-transcribed into DNA and the resulting proviral DNA is integrated into the host genome by the viral integrase enzyme. Once integrated, the provirus is replicated passively with the host cell's DNA during mitosis and can remain latent for extended periods.

Transcription from the provirus by the host RNA polymerase produces viral RNA, which serves as the genome for new virions and as mRNA for viral proteins. Reactivation depends on cellular and environmental cues, and may lead to production of infectious virions.

From the host perspective, a provirus behaves as part of the host genome. Proviruses are common in many organisms; most are remnants of ancient retroviral infections now inherited through the germ line in the case of endogenous retroviruses.

A related concept is the prophage, which is a viral genome integrated into the DNA of a bacterial host. In contrast to episomal viral DNA that exists outside the host genome, proviral DNA is integrated into the genome and replicates with it.

Medical relevance is significant because the proviral stage underpins viral latency and persistent infections. In HIV infection, the proviral reservoir in resting T cells constitutes a major barrier to cure, as latent proviruses can reactivate. Antiretroviral therapy suppresses viral replication but does not remove integrated proviral DNA.