1. The identification of small molecules that alter the activity of the LINE1 endonuclease
Maurice-Walker, L. M.,* 2Ahmad, I. I. 1, Reddix, S. 1, Russell, B. L. 1, Mottamal, M.3,
Huang, Tien L. 4 , and DeFreece C.B1.
High copy mobile repeats, known as retrotransposons, have been of recent interest to many
scientists. These mobile elements are able to replicate and insert DNA within the human genome
by a process known as retrotransposition. Insertions to the genome accrue changes that have
been linked to the development of muscular dystrophy, breast and colon cancer. Long-
interspersed element-1 (LINE1), a specific class of transposon, is autonomous and requires the
endonuclease and reverse transcriptase activities of the protein ORF2. During retrotransposition,
the LINE1 endonuclease binds to a 5‘TTTTAA3’ target sequence, nicks the DNA between the
fourth thymine and the first adenosine, and transcribes a new copy of DNA into the genome.
Further studies characterizing LINE1 endonuclease activity shows that the enzyme induces
formation of a double stranded break (DSB) in the DNA. Only a small percentage of DSBs in the
genome resulting from LINE1 activity can be attributed to retrotransposition events suggesting
that LINE1 activity is more severe than previously considered. Therefore, inhibition of the
enzyme would be beneficial for limiting LINE1-induced genetic instability. To test enzyme
inhibition, in vitro and in silico screenings of small molecules were performed, and verified
using biochemical kinetic assays. We have thus far identified a subset of small molecules that
have been attributed to minimize LINE1 activity.