Provirus
Encyclopedia
A provirus is a virus
genome that is integrated into the DNA
of a host cell
.
This state can be a stage of virus replication, or a state that persists over longer periods of time as either inactive viral infections or an endogenous retrovirus. In inactive viral infections the virus will not replicate itself but through replication of its host cell. This state can last over many host cell generations.
Special viruses - endogenous retroviruses are always in the state of a provirus.
When a (nonendogenous) retrovirus invades a cell, the RNA
of the retrovirus is reverse-transcribed into DNA by reverse transcriptase
, then inserted into the host genome
by an integrase
.
A provirus does not directly make new DNA copies of itself while integrated into a host genome in this way. Instead, it is passively replicated along with the host genome and passed on to the original cell's offspring; all descendants of the infected cell will also bear proviruses in their genomes. Integration can result in a latent infection or a productive infection. In a productive infection, the provirus is transcribed into messenger RNA which directly produces new virus, which in turn will infect other cells. A latent infection results when the provirus is transcriptionally silent rather than active.
A latent infection may become productive in response to changes in the host's environmental conditions or health, the provirus may be activated and begin transcription of its viral genome. This can result in the destruction of its host cell because the cell's protein synthesis machinery is hijacked to produce more viruses.
It is thought that provirus may account for approximately 8% of the human genome in the form of inherited endogenous retrovirus
es.
Examples in human
s include HIV
and HTLV.
A provirus not only refers to a retrovirus but is also used to describe other viruses that can integrate into the host chromosome
s, another example being adeno-associated virus
.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
genome that is integrated into the DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
of a host cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
This state can be a stage of virus replication, or a state that persists over longer periods of time as either inactive viral infections or an endogenous retrovirus. In inactive viral infections the virus will not replicate itself but through replication of its host cell. This state can last over many host cell generations.
Special viruses - endogenous retroviruses are always in the state of a provirus.
When a (nonendogenous) retrovirus invades a cell, the RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
of the retrovirus is reverse-transcribed into DNA by reverse transcriptase
Reverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
, then inserted into the host genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
by an integrase
Integrase
Retroviral integrase is an enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cell...
.
A provirus does not directly make new DNA copies of itself while integrated into a host genome in this way. Instead, it is passively replicated along with the host genome and passed on to the original cell's offspring; all descendants of the infected cell will also bear proviruses in their genomes. Integration can result in a latent infection or a productive infection. In a productive infection, the provirus is transcribed into messenger RNA which directly produces new virus, which in turn will infect other cells. A latent infection results when the provirus is transcriptionally silent rather than active.
A latent infection may become productive in response to changes in the host's environmental conditions or health, the provirus may be activated and begin transcription of its viral genome. This can result in the destruction of its host cell because the cell's protein synthesis machinery is hijacked to produce more viruses.
It is thought that provirus may account for approximately 8% of the human genome in the form of inherited endogenous retrovirus
Endogenous retrovirus
Endogenous retroviruses are sequences in the genome thought to be derived from ancient viral infections of germ cells in humans, mammals and other vertebrates; as such their proviruses are passed on to the next generation and now remain in the genome....
es.
Examples in human
Human
Humans are the only living species in the Homo genus...
s include HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
and HTLV.
A provirus not only refers to a retrovirus but is also used to describe other viruses that can integrate into the host chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s, another example being adeno-associated virus
Adeno-associated virus
Adeno-associated virus is a small virus which infects humans and some other primate species. AAV is not currently known to cause disease and consequently the virus causes a very mild immune response. AAV can infect both dividing and non-dividing cells and may incorporate its genome into that of...
.
See also
- BornavirusBornavirusBorna disease virus is the virus that causes Borna disease.- Genome :It has the smallest genome of any Mononegavirales species and is unique within that order in its ability to replicate within the host cell nucleus....
- ProphageProphageA prophage is a phage genome inserted and integrated into the circular bacterial DNA chromosome. A prophage, also known as a temperate phage, is any virus in the lysogenic cycle; it is integrated into the host chromosome or exists as an extrachromosomal plasmid. Technically, a virus may be called...
- Phage
- RetrotransposonRetrotransposonRetrotransposons are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. They are a subclass of transposon. They are particularly abundant in plants, where they are often a principal component of nuclear DNA...
- GermlineGermlineIn biology and genetics, the germline of a mature or developing individual is the line of germ cells that have genetic material that may be passed to a child.For example, gametes such as the sperm or the egg, are part of the germline...
- Horizontal gene transferHorizontal gene transferHorizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
- Endogenous retrovirusEndogenous retrovirusEndogenous retroviruses are sequences in the genome thought to be derived from ancient viral infections of germ cells in humans, mammals and other vertebrates; as such their proviruses are passed on to the next generation and now remain in the genome....
- Adeno-Associated VirusAdeno-associated virusAdeno-associated virus is a small virus which infects humans and some other primate species. AAV is not currently known to cause disease and consequently the virus causes a very mild immune response. AAV can infect both dividing and non-dividing cells and may incorporate its genome into that of...