Long Interspersed Nuclear Elements (LINEs): Evolution


LINE‐1 (long interspersed nuclear element‐1, L1) repeated deoxyribonucleic acid (DNA) elements are non‐long terminal repeat (LTR) group of retrotransposons that replicate by copying (reverse transcribing) their ribonucleic acid (RNA) transcript into genomic DNA. LINE‐1 elements, which can also copy other RNAs into genomic DNA, are the dominant (and in some species the only) active clade of retrotransposons in mammals, where they have been replicating and evolving since before the mammalian radiation approximately 100 million years ago.

Keywords: LINE‐1; L1; retrotransposon; evolution; human

Figure 1.

LINE‐1 families in the human lineage. (a) A typical human L1 element. The 5′ untranslated region (UTR) has a regulatory function; open reading frame (ORF) I encodes an RNA chaperone (Martin, ); ORF II encodes the L1 replicase containing highly conserved endonuclease (EN) and reverse transcriptase (RT) domains; the 3′ UTR contains a conserved guanine (G)‐rich polypurine motif (filled box). Genomic copies of L1 usually end in an adenine (A)‐rich stretch (see Furano, ). (b) Maximum likelihood tree built on the consensus sequences of ORF II of primate L1 families (Khan et al., ). The L1MA, L1PB and L1PA lineages were concurrently active in the ancestral primate genome from 70 to 40 MYA and each lineage had nonhomologous 5′ UTRs. Reproduced with permission from Khan et al..



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Further Reading

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Furano, Anthony V, and Boissinot, Stéphane(Jul 2008) Long Interspersed Nuclear Elements (LINEs): Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005304.pub2]