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Expert
Reviews in Molecular Medicine: http://www.expertreviews.org/
Accession information: Vol. 8; Issue 5; 6 March 2006 Abstract
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Overview of the transition of the retroviral genome from ss RNA to integrated ds DNA
Alison Sinclair, Sarah Yarranton and Celine Schelcher
Figure 1. Overview of the transition of the retroviral genome from ss RNA to integrated ds DNA. Retroviral virions contain a single-stranded (ss) RNA version of their genome. Upon infection of permissive cells, the ss RNA is converted to double-stranded (ds) DNA by the action of the virion enzyme reverse transcriptase. Reverse transcriptase employs a tRNA molecule bound near the U5 region of the ss RNA genome as an initial primer to synthesise a short region of single-stranded viral DNA, containing U5 and R regions. The DNA then dissociates from the genome and anneals to another copy of the R region, at the 3' end of the genome. DNA synthesis proceeds along the genome to generate the negative strand. The positive strand is replicated from this template by a mechanism that uses DNA as its template and might involve circularised molecules. The RNA primer is destroyed by the RNAse H activity of reverse transcriptase. The double-stranded DNA genome is then recognised by a second virion enzyme, integrase, which cleaves two nucleotides from the 3' end of each DNA strand at the long terminal repeat (LTR) and mediates their ligation into the host DNA. This process leaves the 5' ends of the viral DNA unligated, resulting in single-strand breaks (SSBs).
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