Genetic switches designed for eukaryotic cells and controlled by serine integrases

Recently, new serine integrases have been identified, increasing the possibility of scaling up genomic modulation tools. Here, we describe the use of unidirectional genetic switches to evaluate the functionality of six serine integrases in different eukaryotic systems: the HEK 293T cell lineage, bovine fibroblasts and plant protoplasts. Moreover, integrase activity was also tested in human cell types of therapeutic interest: peripheral blood mononuclear cells (PBMCs), neural stem cells (NSCs) and undifferentiated embryonic stem (ES) cells. The switches were composed of plasmids designed to flip two different genetic parts driven by serine integrases. Cell-based assays were evaluated by measurement of EGFP fluorescence and by molecular analysis of attL/attR sites formation after integrase functionality. Our results demonstrate that all the integrases were capable of inverting the targeted DNA sequences, exhibiting distinct performances based on the cell type or the switchable genetic sequence. These results should support the development of tunable genetic circuits to regulate eukaryotic gene expression. Gomide et al. generate unidirectional genetic switches to test the site-specific recombination function of six recently identified serine integrases in a range of eukaryotic cells. They report that one of the integrases Int13 is as active in vertebrate cells as the currently top performing integrases, Bxb1 and PhiC31.