Fig. 4: Proposed mechanism of action of the iLight optogenetic systems.
From: Single-component near-infrared optogenetic systems for gene transcription regulation
a Schematics of the mCherry gene transcription repression in the iLight bacterial system. Expression of mCherry from the constitutively active ColE promoter with LexA408 operator is controlled by the oligomeric state of iLight fused with DNA-binding domain of LexA408. b Schematics of the reporter gene transcription activation in the iLight mammalian system. To induce reporter expression from the plasmid with 12× (upstream activating sequence) UAS upstream of minimal promoter, a nucleus localization signal (NLS)-tagged iLight was fused with a Gal4 DNA-binding domain and a VP16 transcriptional activation domain. The 660 nm light-induced iLight tetramerization brings the Gal4 DNA-binding domains into proximity, enabling them to bind 12× UAS and allowing VP16 to recruit transcription initiation complexes.
