Characterizing inhibitors of the human mobile element L1 endonuclease

Abstract

The Long interspersed element‐1 (L1) an active autonomous retroelement within the human genome. L1 replicates itself through a process known as retrotransposition. While L1 mutagenic L1 insertion events have been associated with diseases like breast and colon cancer, the full effect of L1 endonuclease activity on the stability of the genome is undetermined. We know that L1 endonuclease expression is associated with a DNA double strand break (DSB) and that the DNA DSB must occur during retrotransposition prior to the integration of novel L1 elements. However, not all of the L1‐associated DNA DSBs are repaired by insertion of a novel L1 element, and the breaks must be repaired faithfully or DNA mutations can occur. Thus, we hypothesize that an inhibitor of L1 endonuclease would be beneficial for estimating L1‐associated damage and to potentially minimize L1‐related genetic instability. We have tested novel small molecules for their ability to inhibit L1 endonuclease using in vitro endonuclease cleavage assays and cell based L1 retrotransposition assays. We have thus far identified a subset of small molecules that inhibit the L1 endonuclease. We are still in the process of confirming these inhibitors through additional testing and locating more inhibitors. Once the inhibitor is located we can begin to answer the question of whether DNA damage associated with the activity of the LINE1 endonuclease leads to mutation and disease.