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.
Rademacher, A., Erdel, F., Trojanowski, J., Schumacher, S., & Rippe, K. (2017). Real-time observation of light-controlled transcription in living cells. Journal of Cell Science, 130(24), 4213–4224. https://doi.org/10.1242/jcs.205534