Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease

The long interspersed nuclear element-1 (LINE-1 or L1) retrotransposon is the only active autonomously replicating retrotransposon in the human genome. L1 harms the cell by inserting new copies, generating DNA damage, and triggering inflammation. Therefore, L1 inhibition could be used to treat many diseases associated with these processes. Previous research has focused on inhibition of the L1 reverse transcriptase due to the prevalence of well-characterized inhibitors of related viral enzymes. Here we present the L1 endonuclease as another target for reducing L1 activity. We have characterized structurally diverse small molecule endonuclease inhibitors using computational, biochemical, and biophysical methods. We also show that these inhibitors reduce L1 retrotransposition, L1-induced DNA damage, and inflammation reinforced by L1 in senescent cells. These inhibitors could be further used to better understand the life cycle of this element and its impact on human health. Human normal diploid lung fibroblast cells were passaged into replicative senescence, the irreversible exit of cells from the cell cycle. Samples were treated in triplicate with vehicle, L1 reverse transcriptase inhibitor 3TC, or L1 endonuclease inhibitor AD12. The gene expression changes of inflammation markers were analyzed in response to inhibitor treatment.