Unusually long target site duplications flanking some of the long terminal repeats of human endogenous retrovirus K in the human genome.

Human endogenous retroviruses (HERVs) make up a substantial part of the human genome. HERVs and solitary long terminal repeats (solo LTRs) are usually flanked by 4-6 nt short direct repeats through the well-known mechanism of their integration. A number of solo LTRs flanked by unusually long direct repeats were detected in the human genome. These unusual structures might be a product of an alternative virus insertion mechanism.