[Endogenous proretroviruses and other autonomous retroposons: traces of viral origin or decay?].

Origin of viruses is considered to be a fundamental trend in biology. In 1970 H. Temin proposed that some of them (namely, retroviruses) could originate from preexisting transcriptional units of cell genome. This "protovirus hypothesis" was supported recently by new findings. It is clear now that eukaryotic genomes contain sequences related to retroviral genes and long terminal repeats. Some endogenous retrovirus-related sequences can be considered to be interstitial stages in retrovirus origin. We suppose that not only retroviruses but all the autonomous retroposons could arise from cellular sequences.