Final Report Summary - CRISPRSYSTEM (Identification and Characterization of Host and Phage Proteins Interacting with the CRISPR System) Our proposal focused on studying novel aspects in a newly discovered bacterial defense system, the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) system. Research on this system in the last seven years, since its discovery, has yielded tremendous insights on its regulation, mechanism, and applications. One breakthrough application of the system is the precise modification of any given DNA molecule, including the human genetic material. Thus, the prospects are high that the system will play a significant role in human health, as well as in significant biotechnological applications. Its potential for advancing biotechnological applications is arguably greater than the tremendous applications enabled by the discovery of restriction enzymes in the late 20th century. We focused in our proposal mainly on basic aspects of the system, but also demonstrated the use of the system for genetic engineering applications in bacteriophages. During the grant period, I managed to establish a highly productive lab that focuses on cutting-edge research in the CRISPR/Cas field. My lab was the first to provide a platform for studying a process that could not be studied till then, the CRISPR adaptation process. We established an experimental system that demonstrated the acquisition process of the bacterial immune system and identified the essential proteins, DNA elements, and key steps in the mechanism of this process. This study was published in Nucleic Acids Research and was already cited ~100 times within two years since its publication. We also re-defined borders of the elements of the CRISPR array in a study published in the Journal of Molecular Biology. Moreover, we identified a novel element in sequences acquired to confer immunity against phages. This element enhances the acquisition of these sequences into the CRISPR array and was published in PNAS. The results leading to these publications were not originally in the proposal, but replaced aims that were proposed by us but completed by a competing group. In another study, also published in PNAS, my group identified a novel protein essential for the CRISPR immunity function, and elucidated its mechanism of action. Another important study showed, for the first time, the activity of the CRISPR/Cas system against lysogens and prophages. This study was published in the Journal of Bacteriology and was cited already 45 times. These last two manuscripts describe the results proposed in one of the major aims of the proposal. Lastly, we managed to describe a system for modifying phage genomes using the CRISPR-Cas system. The published scientific breakthroughs resulting from funding this proposal enabled me to participate as an invited lecturer in three international CRISPR meetings. It enabled me to support a productive team of motivated scientists. In addition, the support boosted my career in that the accomplishments enabled me to secure more grants, such as the prestigious StG-ERC, as well as others. Finally, these achievements granted me tenure in Tel Aviv University, as well as a promotion to Associate Professor. Thus, I believe that the expected career support and scientific achievements were fully met.