SVA elements are nonautonomous retrotransposons that cause disease in humans

L1 elements are the only active autonomous retrotransposons in the human genome. The nonautonomous Alu elements, as well as processed pseudogenes, are retrotransposed by the L1 retrotransposition proteins working in trans. Here, we describe another repetitive sequence in the human genome, the SVA element. Our analysis reveals that SVA elements are currently active in the human genome. SVA elements, like Alus and L1s, occasionally insert into genes and cause disease. Furthermore, SVA elements are probably mobilized in trans by active L1 elements.