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. Author manuscript; available in PMC: 2010 Dec 14.
Published in final edited form as: Gene. 2009 Jun 6;448(2):233–241. doi: 10.1016/j.gene.2009.05.014

Figure 1. Alternative mechanisms of retrotransposon integration.

Figure 1

(a) Classical TPRT-mediated L1 or Alu insertion into the host primate genome. L1 EN creates a nick in the first strand (orange arrow) at the 5′-TTTT/A-3′ consensus and the retrotransposon mRNA (purple line) anneals to the genomic DNA (blue line) using its polyA tail (purple outline). L1 RT (pink oval) synthesizes the retrotransposon mRNA to complete insertion and the TSDs (grey) are filled in. (b) TPRT variant-mediated retrotransposon insertion. L1 RT internally primes on the L1 or Alu mRNA and the break is filled using classical TPRT machinery. (c) Staggered DSB repair with 5′ overhangs. A staggered DSB (lightning bolt) occurs and RT (pink oval) internally primes on the mobile element mRNA (purple line) that bridges the gap by binding to either end. Subsequent cDNA synthesis fills the break with a copy of the truncated element.