Condensation of LINE-1 is critical for retrotransposition
- New York University Langone Medical Center, United States
Abstract
LINE-1 (L1) is the only autonomously active retrotransposon in the human genome, and accounts for 17% of the human genome. The L1 mRNA encodes two proteins, ORF1p and ORF2p, both essential for retrotransposition. ORF2p has reverse transcriptase and endonuclease activities, while ORF1p is a homotrimeric RNA-binding protein with poorly understood function. Here we show that condensation of ORF1p is critical for L1 retrotransposition. Using a combination of biochemical reconstitution and live-cell imaging, we demonstrate that electrostatic interactions and trimer conformational dynamics together tune the properties of ORF1p assemblies to allow for efficient L1 ribonucleoprotein (RNP) complex formation in cells. Furthermore, we relate the dynamics of ORF1p assembly and RNP condensate material properties to the ability to complete the entire retrotransposon life-cycle. Mutations that prevented ORF1p condensation led to loss of retrotransposition activity, while orthogonal restoration of coiled-coil conformational flexibility rescued both condensation and retrotransposition. Based on these observations, we propose that dynamic ORF1p oligomerization on L1 RNA drives the formation of an L1 RNP condensate that is essential for retrotransposition.
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All data generated or analysed during this study are included in the manuscript and supporting files
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Funding
National Institute of General Medical Sciences (R01 GM132447)
- Srinjoy Sil
- Sarah Keegan
- Farida Ettefa
- Lance Denes
- Liam J Holt
National Cancer Institute (R37 CA240765)
- Srinjoy Sil
- Sarah Keegan
- Farida Ettefa
- Lance Denes
- Liam J Holt
Air Force Office of Scientific Research (FA9550-21-1-3503 0091)
- Srinjoy Sil
- Sarah Keegan
- Farida Ettefa
- Lance Denes
- Liam J Holt
National Institute on Aging (P01 AG051449)
- Srinjoy Sil
- Sarah Keegan
- Farida Ettefa
- Lance Denes
- Liam J Holt
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Sil et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Condensation of LINE-1 is critical for retrotransposition
eLife 12:e82991.
https://doi.org/10.7554/eLife.82991
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