A 3′ Poly(A) Tract Is Required for LINE-1 Retrotransposition

• Published in: Molecular cell Vol. 60; no. 5; pp. 728 - 741
• Main Authors: Doucet, Aurélien J., Wilusz, Jeremy E., Miyoshi, Tomoichiro, Liu, Ying, Moran, John V.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03-12-2015
• Subjects: Endonucleases - genetics; HeLa Cells; Humans; Long Interspersed Nucleotide Elements; Poly A - metabolism; RNA, Long Noncoding - metabolism; RNA, Messenger - chemistry; RNA, Messenger - genetics; RNA-Directed DNA Polymerase - genetics
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2015.10.012

L1 retrotransposons express proteins (ORF1p and ORF2p) that preferentially mobilize their encoding RNA in cis, but they also can mobilize Alu RNA and, more rarely, cellular mRNAs in trans. Although these RNAs differ in sequence, each ends in a 3′ polyadenosine (poly(A)) tract. Here, we replace the L1 polyadenylation signal with sequences derived from a non-polyadenylated long non-coding RNA (MALAT1), which can form a stabilizing triple helix at the 3′ end of an RNA. L1/MALAT RNAs accumulate in cells, lack poly(A) tails, and are translated; however, they cannot retrotranspose in cis. Remarkably, the addition of a 16 or 40 base poly(A) tract downstream of the L1/MALAT triple helix restores retrotransposition in cis. The presence of a poly(A) tract also allows ORF2p to bind and mobilize RNAs in trans. Thus, a 3′ poly(A) tract is critical for the retrotransposition of sequences that comprise approximately one billion base pairs of human DNA.
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•The 3′ poly(A) tail of L1 RNA is required for L1 retrotransposition in cis•A 3′ poly(A) tract allows L1 ORF2p to bind and mobilize cellular RNAs in trans•The 3′ poly(A) tracts of L1 and Alu RNAs compete for the binding of L1 ORF2p•A 3′ poly(A) tract is a determinant for generating ∼one-third of human DNA
Doucet et al. demonstrate that a 3′ poly(A) tract is required for human LINE-1-mediated retrotransposition. The ORF2p LINE-1-encoded protein preferentially associates with 3′ poly(A) tracts in LINE-1 and Alu RNAs, which helps explain their abundance in the human genome.