Sleeping Beauty transposon integrates into non-TA dinucleotides via an alternative mechanism

Sleeping Beauty transposon (SB) is an important genetic tool for generating mutations in vertebrates. It is well known that SB exclusively integrates into TA dinucleotides. However, this “TA law” has never been strictly tested in large number of insertion sites after next generation sequencing was widely utilized. In this study, we analyzed 600 million pairs of Illumina sequence reads and identified 28 thousand SB insertions in non-TA sites. We recovered some non-TA sites using PCR and confirmed that at least parts of the insertions at non-TA sites are real integrations. The consensus sequence of these non-TA sites showed an asymmetric pattern distinct from the symmetric pattern of the canonical TA sites. The right side of the consensus sequence is exactly the same as the sequence of SB transposon ends, indicating interaction between the transposon DNA and the target DNA. Based on these results we suggested that SB has an alternative integration mechanism besides the canonical one to integrate its DNA into non-TA sites. Highlights ∼ For the first time, we proved that Sleeping Beauty transposon can integrate into non-TA dinucleotides. ∼ For the first time, we provided evidence that transposon DNA can directly interact with target DNA. ∼ And for the first time, we found that a transposon can have two independent integration mechanisms.