Mammalian Genetic Circuit Construction Utilizing the Q System

It is highly desirable to have additional transcriptional regulatory tools that can be applied independently of existing systems in mammalian cells.  The Q system is a binary expression system that was originally discovered in Drosophila. The regulatory parts have been moved upstream of the fluorescent molecule, GFP, and has been demonstrated to work in Drosophila, C. elegans, and zebrafish. Here the regulatory parts are introduced as a new component for future genetic circuits in mammalian cells. The regulatory component of the Q system contains two genes of interest QF and QS along with the necessary binding sites (QUAS). QF acts as a transactivator for genes downstream of its binding site, while QS inhibits the binding of QF and prevents transcription. The predictable binary manner of the system makes the system a prime candidate for inclusion into the synthetic biology repertoire. To demonstrate the Q system’s candidacy it was introduced to mammalian cells to determine functionality. Plasmids containing QF and binding sites upstream of a reporter gene were found to function as predicted. However, the repression predicted for QS was absent and thus deemed unfit for inclusion in genetic circuits. Additionally, QF and QUAS were coupled with existing components to predictably control gene expression through genetic circuits such as Boolean logic gates and an oscillatory system. The Q system demonstrates its candidacy for inclusion into the synthetic biology repertoire to advance the construction of genetic circuits in a controlled and predictable manner.