Retroviral Replication

The retroviruses (the taxonomic family Retroviridae) comprise isolates of vertebrates, but elements with hallmarks of retroviruses are also found elsewhere, e.g. in insects. Retroviruses exemplify a variety of specialized interactions with their hosts, including induction of many kinds of diseases under laboratory conditions as well as in domestic and wild animals. In contrast to this variation in biological properties, all retroviruses share the same basic genomic organization and a mode of replication by which the ribonucleic acid (RNA) genome of viral particles is reverse transcribed into a deoxyribonucleic acid (DNA) form, the provirus, in the infected cell. Virus particles have a diameter of about 100 nm; a lipid envelope surrounds a core of structural and catalytic proteins, including the enzymes reverse transcriptase (RT) that copies the RNA genome into double-stranded DNA and integrase (IN) that catalyses integration of the double-stranded viral DNA into host chromosomal DNA (Figure 1a). During the past few decades retroviruses have received more scientific attention than any other group of animal viruses. While basic genome organization and replication mechanisms were defined in model viruses such as Rous sarcoma virus and Moloney murine leukemia virus, today the most intensively studied retrovirus is the human pathogen, the Human immunodeficiency virus type 1 (HIV-1).