L1 retrotransposons have been replicating and evolving in mammals since ≥ 80 million years ago and have generated at least 40% of their genomes. Novel L1 families repeatedly arose, only to go extinct coincident with the emergence of another novel L1 family. This pattern has persisted to the present despite the fact that L1 activity is deleterious to its host.

The pattern of mammalian L1 evolution resembles that of the influenza virus HA antigen in humans. The latter is explained by the successive emergence of viral variants that bypass existing host defenses (immunity) followed by the reestablishment of host immunity. We suggest that an analogous adversarial interaction between L1 and its host could explain the pattern of L1 evolution.

Projects that examine the interaction of L1 and its host:

• Determine host factors that interact with regions of L1 that have been either highly conserved or undergone adaptive evolution.
  
  
• Analysis of the structural and functional consequences of adaptive changes undergone by L1 encoded proteins.

To apply:

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