# Biology and utilization of R2 retrotransposons

## TL;DR

This paper reviews R2 retrotransposons, their unique ability to insert into specific genomic sites, and their potential as tools for genome engineering.

## Contribution

The paper highlights recent advances in using R2 retrotransposons for targeted gene integration and their potential as biotechnological tools.

## Key findings

- R2 retrotransposons insert into ribosomal DNA using a precise mechanism called target-primed reverse transcription.
- The R2-encoded protein has multiple functions including reverse transcriptase and endonuclease activities.
- R2 elements are being explored as novel tools for targeted gene integration in genome engineering.

## 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.