Curated Optogenetic Publication Database

Abstract: Gene expression is tightly regulated in space and time. To dissect this process with high temporal resolution, we introduce an optogenetic tool termed blue light-induced chromatin recruitment (BLInCR) that combines rapid and reversible light-dependent recruitment of effector proteins with a real-time readout for transcription. We used BLInCR to control the activity of a cluster of reporter genes in the human osteosarcoma cell line U2OS by reversibly recruiting the viral transactivator VP16. RNA production was detectable ∼2 min after VP16 recruitment and readily decreased when VP16 dissociated from the cluster in the absence of light. Quantitative assessment of the activation process revealed biphasic activation kinetics with a pronounced early phase in cells treated with the histone deacetylase inhibitor SAHA. Comparison with kinetic models of transcription activation suggests that the gene cluster undergoes a maturation process when activated. We anticipate that BLInCR will facilitate the study of transcription dynamics in living cells.This article has an associated First Person interview with the first author of the paper.

Abstract: Cells depend on the proper positioning of their organelles, suggesting that active manipulation of organelle positions can be used to explore spatial cell biology and to restore cellular defects caused by organelle misplacement. Recently, blue-light dependent recruitment of specific motors to selected organelles has been shown to alter organelle motility and positioning, but these approaches lack rapid and active reversibility. The light-dependent interaction of phytochrome B with its interacting factors has been shown to function as a photoswitch, dimerizing under red light and dissociating under far-red light. Here we engineer phytochrome domains into photoswitches for intracellular transport that enable the reversible interaction between organelles and motor proteins. Using patterned illumination and live-cell imaging, we demonstrate that this system provides unprecedented spatiotemporal control. We also demonstrate that it can be used in combination with a blue-light dependent system to independently control the positioning of two different organelles. Precise optogenetic control of organelle motility and positioning will provide a better understanding of and control over the spatial biology of cells.

Abstract: Light-sensitive proteins are useful tools to control protein localization, activation and gene expression, but are currently limited to excitation with red or blue light. Here we report a novel optogenetic system based on the ultraviolet-B-dependent interaction of the Arabidopsis ultraviolet-B photoreceptor UVR8 with COP1 that can be performed in visible light background. We use this system to induce nuclear accumulation of cytoplasmic green fluorescent protein fused to UVR8 in cells expressing nuclear COP1, and to recruit a nucleoplasmic red fluorescent protein fused to COP1 to chromatin in cells expressing UVR8-H2B. We also show that ultraviolet-B-dependent interactions between DNA-binding and transcription activation domains result in a linear induction of gene expression. The UVR8-COP1 interactions in mammalian cells can be induced using subsecond pulses of ultraviolet-B light and last several hours. As UVR8 photoperception is based on intrinsic tryptophan residues, these interactions do not depend on the addition of an exogenous chromophore.