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Tumor suppressor proteins restricts LINE-1 retrotransposition


Long interspersed element 1 (LINE-1) is a retroelement comprising about 17% of the human genome, encoding ORF1 with an RNA interaction domain and ORF2 with endonuclease and reverse transcriptase activities. Similar to retroviruses, LINE-1 replicates in the host via an RNA intermediate that is reverse transcribed and integrated into the host genome. LINE-1 retrotransposition has resulted in genetic diseases. In fact, LINE-1 insertion was recently found in several human tumors. However, the life cycle of LINE-1 is not fully understood. Therefore, we examined identification and characterization of host factors affected the retrotransposition of LINE-1.

Materials and methods

We used the pL1RP-EGFP plasmid, which contains an enhanced green fluorescent protein (EGFP)-based retrotransposition detector cassette. The retrotransposition rate of LINE-1 in 293T cells was determined by flow cytometry after the cotransfection of pL1RP-EGFP with plasmids expressing DEAD-box RNA helicases (DDX1, DDX3, DDX5, DDX6, DDX17, DDX21, and DDX56), cancer related proteins (p53, p21, Pin1 and PML isoforms I-VI) or P-body components (MOV10, Ago2, APOBEC3F, and APOBEC3G). We observed the subcellular localizations of LINE-1 ORF1 protein and host factors by using confocal laser scanning microscopy. We also examined immunoprecipitation to analyzed the interaction of LINE-1 ORF1 with the host factor(s).


We found that MOV10 markedly inhibited the retrotransposition of LINE-1 as well as APOBEC3G/F. Accordingly, LINE-1 ORF1 colocalized with MOV10 or APOBEC3G in P-bodies. In addition, LINE-1 ORF1 was also found in stress granules induced after the treatment with 0.5mM NaAsO2 for 30 minutes, indicating that LINE-1 ORF1 is both P-body and stress granule component. Furthermore, immunoprecipitation analysis showed that MOV10 and APOBEC3G bound to LINE-1 ORF1, suggesting the inhibitory mechanism. Moreover, we noticed that DDX3, PML IV, p53, p21, Pin1, and Ago2 significantly inhibited the retrotransposition of LINE-1.


We identified several host factors, including MOV10, DDX3, PML IV, p53, p21, Pin1, and Ago2 as the restriction factors of LINE-1. Thus, several tumor suppressor proteins seem to restrict LINE-1 retrotransposition.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Kuroki, M., Yasuda-lnoue, M., Nakashima, S. et al. Tumor suppressor proteins restricts LINE-1 retrotransposition. Retrovirology 10 (Suppl 1), P43 (2013).

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