Testing the retroelement invasion hypothesis for the emergence of the ancestral eukaryotic cell

Gloria Lee, Nicholas A. Sherer, Neil H. Kim, Ema Rajic, Davneet Kaur, Niko Urriola, K. Michael Martini, Chi Xue, Nigel Goldenfeld, Thomas E. Kuhlman

Research output: Contribution to journalArticlepeer-review


Phylogenetic evidence suggests that the invasion and proliferation of retroelements, selfish mobile genetic elements that copy and paste themselves within a host genome, was one of the early evolutionary events in the emergence of eukaryotes. Here we test the effects of this event by determining the pressures retroelements exert on simple genomes. We transferred two retroelements, human LINE-1 and the bacterial group II intron Ll.LtrB, into bacteria, and find that both are functional and detrimental to growth. We find, surprisingly, that retroelement lethality and proliferation are enhanced by the ability to perform eukaryotic-like nonhomologous end-joining (NHEJ) DNA repair. We show that the only stable evolutionary consequence in simple cells is maintenance of retroelements in low numbers, suggesting how retrotransposition rates and costs in early eukaryotes could have been constrained to allow proliferation. Our results suggest that the interplay between NHEJ and retroelements may have played a fundamental and previously unappreciated role in facilitating the proliferation of retroelements, elements of which became the ancestors of the spliceosome components in eukaryotes.

Original languageEnglish (US)
Pages (from-to)12465-12470
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number49
StatePublished - Dec 4 2018


  • Evolution
  • Introns
  • Junk DNA
  • LINE-1
  • Retroelements

ASJC Scopus subject areas

  • General


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