Day 1 :
University Stuttgart, Germany
Keynote: Design of synthetic epigenetic circuits exhibiting positive feedback, memory effects and reversible switching
Time : 10:00-10:45
Albert Jeltsch finished his PhD on Restriction Endonucleases at University Hannover in 1994. Afterwards, he started working on DNA Methyltransferases at Justus-Liebig University Giessen and at the Jacobs University Bremen. Since 2011, he is a Professor of Biochemistry at the University Stuttgart. He is the recipient of the Gerhard-Hess award (DFG) and BioFuture award (BMBF). He has long standing expertise in the biochemical study of DNA and protein methyltransferases, methyl lysine reading domains and in rational and evolutionary protein design. His work has been published in >200 publications in peer reviewed journals and is in the editorial boards of several journals.
We report here the design and experimental validation of synthetic epigenetic memory systems which store information in form of DNA methylation patterns in live bacteria. Key components are a DNA methylation sensitive engineered zinc finger protein controlling a memory operon comprising the CcrM methyltransferase gene and a reporter gene. In the off-state, the memory operon is repressed by the zinc finger protein. It can be triggered by heat, nutrients, UV irradiation or DNA damaging compounds which induce DNA methylation by CcrM. In the induced on-state, methylation marks set in the operator region of the memory operon permanently activate the memory system even after cessation of the trigger signal (positive feedback). Inclusion of a protein degradation tag allowed to establish a reversible switching system. Epigenetic memory switches represent a novel application in synthetic biology with numerous potential applications, for example to set up life biosensors for long term observation of environmental sites for pollution, to ensure cooling chains, as a death switch in containment systems for GMOs, or as cost efficient induction switch in industrial protein production. The large variety of DNA-(adenine-N6)-MTases potentially allows for massive multiplexing of signal storage and potential logical operations depending on more than one input signal.
Institute of Biophysics of CAS, Czech Republic
Time : 10:45-11:30
Martin Falk has completed his PhD from Masaryk University in Brno, CR. He is the Head of the Department of Cell Biology and Radiobiology at the Institute of Biophysics of the Czech Academy of Sciences (Brno, CR). He has authored about 40 papers and book chapters that concern the role of chromatin structure in regulation of cellular processes and biological effects of different types of ionizing radiation. Current research interests include DNA damage and repair, carcinogenesis, tumor cells radio-sensitization, and radiobiology.
Many tumors are resistant to current radiotherapy while ion beam cancer therapy (IBCT) and metal nanoparticles may allow for partial overcoming of this problem. Accelerated ions provide superior therapeutic results over gamma-rays since they are able of inducing complex DNA damages that can be repaired only with difficulty by tumor cells; accelerated ions can also be better focused to the tumor due to energy deposition characteristics (Bragg peak). Selective targeting of radiation effects to tumors can further be improved by metal nanoparticles, such as gadolinium, gold, or platinum nanoparticles studied in our work. These nanoparticles are preferentially internalized by tumor cells and have been recognized to locally amplify the radiation dose upon irradiation. Hence, nanoparticles delivered in tumor cells might increase tumor-specificity and efficiency of radiotherapy at the same time. Importantly, though physical mechanisms related to radiation dose amplification by nanoparticles have been already well described, cellular structures targeted by nanoparticles remain unknown. In this work, we will first discuss biological effects of different kinds of ionizing radiations on normal and tumor cells. Consequently we are going to present quite surprising results on a possible mechanism of nanoparticles-mediated radiosensitization: Under the conditions where 2 nm gadolinium nanoparticles amplify the radiation effects, they remain localized in the cytoplasm and their influence on DSB induction and repair is not significant. This suggests that the radiosensitization mediated by gadolinium and potentially (some) other nanoparticles (of defined parameters) are a cytoplasmic event that is independent of the nuclear DNA breakage, commonly accepted as the main cause of radiation-induced cell killing. Based on recognized intracellular localization of nanoparticles studied, we hypothesize about possible non-DNA targets for (some) nanoparticles.