Editing Retrovirus (section)

=== Genomic structure ===
The retroviral genome is packaged as viral particles. These viral particles are dimers of single-stranded, positive-sense, linear RNA molecules.<ref name=":0" />

Retroviruses (and [[Ortervirales|orterviruses]] in general) follow a layout of 5'–''gag''–''pro''–''pol''–''env''–3' in the RNA genome. ''gag'' and ''pol'' encode polyproteins, each managing the capsid and replication. The ''pol'' region encodes enzymes necessary for viral replication, such as reverse transcriptase, protease and integrase.<ref>Peters, P. J., Marston, B. J., Weidle, P. J., & Brooks, J. T. (2013). Human Immunodeficiency Virus Infection. Hunter's Tropical Medicine and Emerging Infectious Disease, 217–247. doi:10.1016/b978-1-4160-4390-4.00027-8</ref> Depending on the virus, the genes may overlap or fuse into larger polyprotein chains. Some viruses contain additional genes. The lentivirus genus, the spumavirus genus, the HTLV / bovine leukemia virus (BLV) genus, and a newly introduced fish virus genus are retroviruses classified as complex. These viruses have genes called accessory genes, in addition to gag, pro, pol and env genes. Accessory genes are located between pol and env, downstream from the env, including the U3 region of LTR, or in the env and overlapping portions. While accessory genes have auxiliary roles, they also coordinate and regulate viral gene expression.
In addition, some retroviruses may carry genes called oncogenes or onc genes from another class. Retroviruses with these genes (also called transforming viruses) are known for their ability to quickly cause tumors in animals and transform cells in culture into an oncogenic state.<ref>{{cite book |last1=Coffin |first1=John M. |last2=Hughes |first2=Stephen H. |last3=Varmus |first3=Harold E. | name-list-style = vanc |title=Retroviruses |date=1997 |publisher=Cold Spring Harbor Laboratory Press |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK19370/ |language=en |chapter=Genetic Organization |isbn= 978-0-87969-571-2 }}</ref>

The polyproteins are cleaved into smaller proteins each with their own function. The nucleotides encoding them are known as ''subgenes''.<ref name="pmid26800882"/>