FIG 1.

General principle for the control of bacterial gene expression using reprogrammed CRISPR effectors. (A) Guide RNAs form complexes with natural or engineered CRISPR effectors. This results in a programmable ribonucleoprotein complex that will bind to either homologous DNA or RNA depending on the effector type. (B) Gene repression is possible by targeting either the promoter, the coding sequence, or mRNA. Gene activation is possible by fusing dCas9 to a transcriptional activator (such as ω, SoxS, or AsiA) and addressing it to a precise location upstream of the promoter.