IS110 transposons are a large, diverse family of bacterial insertion sequences (IS elements)—small, mobile DNA elements that can move from one genomic location to another. They have recently attracted broad interest due to the finding that some of these transposons use a bridge RNA (bRNA) to recognize both donor DNA and target DNA.
Upon this discovery, researchers hoped that bRNA-guided transposon systems could offer a genome-editing strategy distinct from classical CRISPR-Cas nucleases and thereby enable programmable DNA integration. However, it remained unclear how IS110 elements insert donor DNA into target sites and whether these elements rely on one or multiple reaction pathways.
Now, a new study led by XUE Chaoyou from the Tianjin Institute of Industrial Biotechnology of the Chinese Academy of Sciences, in collaboration with LOU Huiqiang at China Agricultural University and RAO Shuquan from the Chinese Academy of Medical Sciences, answers these questions by showing that RNA-guided IS110 transposons use two mechanistically distinct pathways to mobilize DNA.
The study, which provides a new framework for understanding IS110 transposition and for developing programmable genome-editing tools, was published in Molecular Cell on June 11.
Using the Caz IS110-1 transposon from Caloranaerobacter azorensis , the researchers identified two RNA-guided pathways, demonstrating that IS110 transposition does not follow the previously proposed classical "cut-out-paste-in" model.
In one pathway, guided by full-length bRNA, the transposon generates a figure-eight DNA intermediate rather than the conventional circular DNA intermediate previously thought to characterize IS110 transposition. The intermediate is subsequently resolved by host replication.
The other route is a previously unrecognized "direct-transfer" pathway, in which the transposon DNA is transferred directly to the RNA-specified target site without forming a conventional DNA intermediate.
The researchers further showed that IS110 transposition is controlled by a composite catalytic center formed by the RuvC-like catalytic core of the transposase and a conserved serine residue in the Tnp domain. This catalytic architecture coordinates DNA cleavage and strand-transfer reactions during transposition.
Together, these findings reveal unexpected mechanistic diversity in RNA-guided transposition and clarify how IS110 elements mobilize DNA. The work provides an important foundation for engineering IS110 systems as programmable, next-generation genome-editing tools.
Molecular Cell
Experimental study
Not applicable
IS110 transposon utilizes two mechanistically distinct RNA-guided transposition pathways
1-Jun-2026