Bikard, DavidJiang, WenyanSamai, PoulamiHochschild, AnnZhang, FengMarraffini, Luciano A.2014-03-012013Bikard, David, Wenyan Jiang, Poulami Samai, Ann Hochschild, Feng Zhang, and Luciano A. Marraffini. 2013. “Programmable repression and activation of bacterial gene expression using an engineered CRISPR-Cas system.” Nucleic Acids Research 41 (15): 7429-7437. doi:10.1093/nar/gkt520. http://dx.doi.org/10.1093/nar/gkt520.0305-1048http://nrs.harvard.edu/urn-3:HUL.InstRepos:11855878The ability to artificially control transcription is essential both to the study of gene function and to the construction of synthetic gene networks with desired properties. Cas9 is an RNA-guided double-stranded DNA nuclease that participates in the CRISPR-Cas immune defense against prokaryotic viruses. We describe the use of a Cas9 nuclease mutant that retains DNA-binding activity and can be engineered as a programmable transcription repressor by preventing the binding of the RNA polymerase (RNAP) to promoter sequences or as a transcription terminator by blocking the running RNAP. In addition, a fusion between the omega subunit of the RNAP and a Cas9 nuclease mutant directed to bind upstream promoter regions can achieve programmable transcription activation. The simple and efficient modulation of gene expression achieved by this technology is a useful asset for the study of gene networks and for the development of synthetic biology and biotechnological applications.en-USJournal Article2014-03-0110.1093/nar/gkt520