An oncovirus is a virus associated with cancer. The human immunodeficiency virus (HIV) A bacteriophage virus A virus is a submicroscopic parasitic particle that infects cells in biological organisms. ... When normal cells are damaged beyond repair, they are eliminated by apoptosis. ...

Oncoviruses come in two different forms: viruses with a DNA genome, such as adenovirus, and viruses with an RNA genome, like the Human T-cell Leukemia viruses and several viruses known to be common in cats, mice and chickens. The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Genera Mastadenovirus Aviadenovirus Atadenovirus Siadenovirus Adenoviruses are viruses of the family Adenoviridae. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Leukemia (leukaemia in Commonwealth English) is a cancer of the blood or bone marrow characterized by an abnormal proliferation of blood cells, usually white blood cells (leukocytes). ...

Some oncogenic retroviruses, cancer-causing viruses with RNA genomes, incorporate their genome into the host cell using reverse transcriptases to make DNA. This DNA gets inserted into the cell DNA along with powerful promoter sequences (LTRs) that promote transcription of the viral DNA to reproduce more virus. However, sometimes the viral DNA incorporates a section of the host DNA which contains genes for growth promotion. These growth genes, sometimes called proto-oncogenes in their normal state, become oncogenic once incorporated into the viral DNA because of the increased transcription caused by the viral LTRs. This causes increased growth of the infected cell, leading to cellular proliferation and the formation of tumors. Numerous oncogenes have been discovered in the genomes of transforming retroviruses. Ribonucleic acid (RNA) is a nucleic acid polymer consisting of covalently bound nucleotides. ...

Other oncogenic retroviruses transform cells by integrating into the host gene near a proto-oncogene. If the viral LTRs are close enough to that oncogene, they will upregulate transcription not only of the viral DNA but of the proto-oncogene nearby, causing growth, cell proliferation, and tumor formation.

See also

• carcinogen
• oncogenic