Thumbnail image of graphical abstract

Increased jumping contributes to aging. During aging, normally silenced endogenous retrotransposable elements (RTEs) may get activated. On pages 1035–1043 John Sedivy et al. hypothesize that the ensuing active transposition and associated genome destabilization may be an important molecular process contributing to aging. Long interspersed nuclear elements (LINEs), such as the mammalian L1, constitute one group of RTEs, and recent data demonstrate that L1 copy number increases in senescent fibroblasts. The exact mechanisms triggering these events, however, still remain to be elucidated. The cover shows the L1 nucleoprotein complex (RNA in green, protein in orange) attacking the target DNA.