With the advent of synthetic biology, a lot of synthetic circuits are designed every now and then. These circuits contain a lot of components working in harmony to regulate the gene expression. In any system, as the number of components which work together increases, the need for those components to be orthogonal also increases. The components, if interfere with the working of each other, may cause the system as a whole to fail. Such systems succumb to the noise and growth-related factors present in the biological environment. Recombinases in a biological system are adept at this job and hence, are a good basis for the formation of large-scale networks. Utilizing serine recombinases in such biological circuits provides a solution to these problems, as they have non-identical recognition sites and a particular recombinase works orthogonally to other recombinases.
These allow us to build complex circuits with genetic modification in relatively uncomplicated configurations owing to the small size of attB and attP sites(~50bp). The attP and attB sites (and thus the integrase-att complexes) have imperfect two-fold symmetry. Hence they allow recombination in two different ways, with the sites aligned in ‘parallel’ or ‘antiparallel’ configuration. Thus, the ability to integrate/excise the DNA provides flexibility in the design of the constructs.
We at iGEM IIT Delhi made use of serine based recombinases - Bxb1 and TP901 to develop 2 recombinase-based incoherent feed-forward loop constructs. These constructs show a strong capability for regulating and reducing the expression variability of genes being transcribed in addition to faster response time compared to transcriptional networks. These constructs can be utilized in the development of complex circuits.