title: Essential motifs in the 3' untranslated region required for retrotransposition and the precise start of reverse transcription in non-long-terminal-repeat retrotransposon SART1.
abstract: Non-long-terminal-repeat (non-LTR) retrotransposons amplify their copies by reverse transcribing mRNA from the 3' end, but the initial processes of reverse transcription are still unclear. We have shown that a telomere-specific non-LTR retrotransposon of the silkworm, SART1, requires the 3' untranslated region (3' UTR) for retrotransposition. With an in vivo retrotransposition assay, we identified several novel motifs within the 3' UTR involved in precise and efficient reverse transcription. Of 461 nucleotides (nt) of the 3' UTR, the central region, from nt 163 to nt 295, was essential for SART1 retrotransposition. Of five putative stem-loops formed in RNA for the SART1 3' UTR, the second stem-loop (nt 159 to 221) is included in this region. Loss of the 3' region (nt 296 to 461) in the 3' UTR and the poly(A) tract resulted in decreased and inaccurate reverse transcription, which starts mostly from several telomeric repeat-like GGUU sequences just downstream of the second stem-loop. These results suggest that short telomeric repeat-like sequences in the 3' UTR anneal to the bottom strand of (TTAGG)(n) repeats. We also demonstrated that the mRNA for green fluorescent protein (GFP) could be retrotransposed into telomeric repeats when the GFP coding region is fused with the SART1 3' UTR and SART1 open reading frame proteins are supplied in trans.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bioscience Building 501, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Mizuko
authors.initials: M
authors.lastname: Osanai
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kenji K
authors.initials: KK
authors.lastname: Kojima
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Hamada
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Fujiwara
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002460:Cell Line; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D017924:Nucleopolyhedroviruses / Q000235:genetics; D012313:RNA / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D018626:Retroelements / Q000235:genetics*; D017384:Sequence Deletion; D018411:Spodoptera; D016615:Telomere / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; D008164:Luminescent Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D018626:Retroelements; D049452:Green Fluorescent Proteins; D012313:RNA