Fig. 5

A higher percentage of expressed L1 loci are polymorphic and intronic. a The structure of a functional full length L1 consists of a 5’UTR, containing the endogenous L1 promoter and an antisense promoter, two ORFs encoding proteins required for retrotransposition and a 3’UTR, is ~ 6 kb in length and insertions are usually flanked by TSDs. The expanded 5’UTR cartoon illustrates features of this region, which include a CpG island and the following transcription factor binding sites YY1, RUNX3 and SRY. b The percentage of expressed L1s and not expressed L1s that have the following defining characteristics: polymorphic, intact, intronic and the presence of the following conserved transcription factor binding sites YY1, RUNX3 and SRY. **p < 0.01, ***p < 0.001, TSDs target site duplications, UTR untranslated region, ORF open reading frame