【摘 要】
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Background: LINE-1 (Long Interspersed Nucleotide Elements, L 1), an autonomous retrotransposon, is transiently activated in early stage of embryonic development and continuously activity in tumor test
【机 构】
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The College of Life Sciences and Bio-engineering Beijing Jiaotong University China
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Background: LINE-1 (Long Interspersed Nucleotide Elements, L 1), an autonomous retrotransposon, is transiently activated in early stage of embryonic development and continuously activity in tumor tested so far.The full-length L1 consists of a 5 untranslated region (5-UTR) that encompasses a sense promoter (SP) and a antisense promoter (ASP), two open reading frames (ORF 1 and ORF2) and a 3 untranslated region (3-UTR).The transcripts derived from SP and ASP of 5-UTR implicate to generate a double-strand RNA (dsRNA), a precursor of siRNA, by which executes a feedback regulation.Results: With luciferase report system, the full-length and truncated L1-5UTR was investigated for its sense-and antisense-promoter activities by removing SV40 promoter in recombinant plasmids.The activities of sense promoter (SP) is equal to SV40 and antisense promoter (ASP) is quite weak.Notably, SP activity in truncated L1-5UTR was high by comparing with full-length L1-5UTR,which may account for that the sequence in downstream of L1-5UTR impairs SP activity.The mechanism by which implicates a dsRNA-mediated regulation.By down-regulating Ago2, the feedback regulation mediated by dsRNA in L1-5UTR is elucidated and the function of L1ORF1p in this process was observed, Consequently, the interaction of L1-ORF1p with either Agol or Ago2 or Ago3 or Ago4 was identified by co-immunoprecipitation.Conclusion: Both SP and ASP activities are identified in L1-5UTR and the feedback mediated by dsRNA is a fine-tune regulation for L1-5UTR promoter activity.Ago2, at least as one component, is involved in this process.L1-ORF1p, a RNA binding protein interacting with either Agol or Ago2 or Ago4, is probably responsible for negative regulation of SP activity in L1-5UTR.
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