Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2025 Dec;22(1):1-8.
doi: 10.1080/15476286.2025.2521890. Epub 2025 Jun 25.

Biology and utilization of R2 retrotransposons

Shengqiu Luo  1   2 , Qicheng Chen  1   2 , Yangcan Chen  1   3 , Wei Li  1   2   3
Affiliations
Review

Biology and utilization of R2 retrotransposons

Shengqiu Luo et al. RNA Biol. 2025 Dec.

Abstract

R2 elements serve as a class of non-long terminal repeat (non-LTR) retrotransposons found in animal genomes that specifically insert into the ribosomal DNA (rDNA) sequences of host genomes. Each R2 element contains a single open reading frame (ORF) encoding a multifunctional protein with nucleic acid-binding, reverse transcriptase, and endonuclease activities, enabling specific genomic integration via a mechanism called target-primed reverse transcription (TPRT). As a classical model for studying retrotransposition mechanisms, R2 elements possess unique biological properties and precise integration capabilities, which have inspired novel genome engineering strategies. In this review, we summarize the components and integration mechanisms of R2 retrotransposons and highlight the recent advances in employing these mobile elements for targeted gene integration. Finally, we present future directions for the utilization of R2 retrotransposons as novel biotechnological tools.

Keywords: R2 retrotransposons; RNA; gene integration; genome engineering; mechanism; protein domains; reverse transcription; ribozyme.

PubMed Disclaimer

Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Components of R2 retrotransposons from clades A to D.
Figure 2.
Figure 2.
Schematic of R2 integration model.
Figure 3.
Figure 3.
Application of R2 retrotransposons for gene integration.
See this image and copyright information in PMC

References

    1. Dawid IB, Rebbert ML.. Nucleotide sequences at the boundaries between gene and insertion regions in the rDNA of drosophila melanogaster. Nucleic Acids Res. 1981;9(19):5011–5020. doi: 10.1093/nar/9.19.5011 - DOI - PMC - PubMed
    1. Roiha H, Miller JR, Woods LC, et al. Arrangements and rearrangements of sequences flanking the two types of rDNA insertion in D. melanogaster. Nature. 1981;290(5809):749–754. doi: 10.1038/290749a0 - DOI - PubMed
    1. Smith VL, Beckingham K. The intron boundaries and flanking rRNA coding sequences of Calliphora erythrocephala rDNA. Nucleic Acids Res. 1984;12(3):1707–1724. doi: 10.1093/nar/12.3.1707 - DOI - PMC - PubMed
    1. Fujiwara H, Ogura T, Takada N, et al. Introns and their flanking sequences of Bombyx mori rDNA. Nucleic Acids Res. 1984;12(17):6861–6869. doi: 10.1093/nar/12.17.6861 - DOI - PMC - PubMed
    1. Burke WD, Calalang CC, Eickbush TH. The site-specific ribosomal insertion element type II of Bombyx mori (R2Bm) contains the coding sequence for a reverse transcriptase-like enzyme. Mol Cell Biol. 1987;7(6):2221–2230. doi: 10.1128/MCB.7.6.2221 - DOI - PMC - PubMed

LinkOut - more resources