An introduction to transposase (jumping genes) systems

Class II transposable elements (TEs) are transposons or “jumping genes” that do not require reverse transcription of RNA (unlike Class I TEs). Their movement is mediated by transposase enzymes. Autonomous DNA transposons encode for the enzyme and thus allow independent excision and insertion of the DNA sequence. Non-autonomous DNA transposons do not encode for transposase, and therefore require the presence of another TE that does. Importantly, different transposons insert their genetic sequences into different target sites.  

At least four different families of transposases (based on their catalytic nuclease domains) have been studied: RNase H-like transposases, or DD(E/D) enzymes; UH single-stranded DNA transposases; serine transposases; and tyrosine transposases [1]. Some of the mechanistic aspects of gene movement are similar across these enzyme classes, while others are distinct for each group.  

DNA transposons have numerous applications in biological research and biopharmaceutical development and manufacturing. As mutagenic elements, they are useful for detecting loss-of-function or gain-of-function mutations and generating transgenic animals.  They also have potential to serve as alternatives to viral vectors for delivery of genetic material in gene and gene-modified cell therapies. 

For cell line engineering, transposons are included as part of recombinant protein expression vectors. These DNA transposons contain the gene(s) of interest (GOI) to be inserted into the host cell in between transposase-recognizing inverted terminal repeat (ITR) sequences. Examples of transposon systems used in cell-line engineering include Sleeping Beauty, Tol2, and piggyBac. Each has different integration properties, and some are available in hyperactive versions with much higher activities. 

Lonza’s proprietary GS piggyBac® transposon technology, leverages a hyperactive, engineered transposase designed to excise and insert piggyBac® transposons. The system pastes the expression vector cargo into sites of open chromatin within the host-cell genome, which are highly transcriptionally active sites that are associated with long-term, stable, high expression. 

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  Reference 

1. Hickman, B. and Dyda, F. Mechanisms of DNA Transposition. Microbial Spectr. 3(2) (2015). DOI:  10.1128/microbiolspec.MDNA3-0034-2014