Team:Penn/LightActivatedOverview

In order to develop a module for light activated cell lysis, we had to implement two elements:

1. A light-activation system that can express a gene of interest
2. A cytotoxic protein that can be expressed as our therapeutic drug to lyse cancer sells

After reading many papers to select an appropriate light-sensing system to use, we selected the YF1/FixJ blue light system. We had also considered the red light sensor Cph8 but ultimately decided on YF1/FixJ because of its high on/off ratio of gene expression and also because of its availability to us (we were fortunate enough to come across the YF1/FixJ system in the form of the pDawn plasmid from the Moglich lab in Germany).

As shown below in Figure 1, the YF1/FixJ system works through a "repress the repressor" concept. Upon 480 nm blue light illumination, YF1 (a fusion of a LOV protein domain and a histidine kinase) phosphorylates a FixJ response regulator that activates the pFixK2 promoter. The activation of pFixK2, promotes expression of the cI repressor that, in turn, represses the lambda promoter pR. The net result is activation of the gene in the downstream MCS.