HIV-1 as RNA evolution machine.

We have over the years studied several sequence or structural elements within the HIV-1 RNA genome. Molecular mechanisms have been proposed for the role of these RNA motifs in virus replication. We have developed HIV-1 evolution as a powerful research method to study different aspects of the viral replication cycle. In this manuscript, I will illustrate the unique capacity of this method to reveal new mechanistic information about viral replication strategies. Examples of HIV-1 RNA evolution that were presented at the 2009 Cantoblanco meeting in Madrid will be discussed, ranging from the control of HIV-1 splicing by RNA structure to the role of cellular tRNA molecules as adaptors in an unusual HIV-1 recombination event, and from regulation of polyadenylation by RNA structure to viral escape from therapeutic pressure imposed by antiviral RNA interference.