Transcription Activator-like Effectors: Adding Another Layer to the Onion of Bacterial Gene Regulation

Over the past decade, novel trans-acting regulatory elements that can be reprogrammed to repress any desired gene of interest have been discovered. The flexibility offered by these trans-regulators has the potential to revolutionize the fields of synthetic biology and metabolic engineering by allowing researchers to create layers of synthetic regulation overtop of endogenous regulatory mechanisms. One such trans-regulatory element is the class of proteins known as Transcription Activator-Like Effectors (TALEs). These proteins, which were originally identified as virulence factors in plant pathogenic bacteria, have gained traction in biotechnology applications due to their customizable DNA binding specificity. Here, we demonstrate that a TALE designed to bind the lac operator is able to inhibit transcription initiation in E. coli. We have also developed a TALE induction system mediated by protein degradation. By expressing a site-specific protease any TALE of interest constructed using our novel scaffold can be degraded, thereby promoting target gene expression. Understanding the attributes of TALEs as well as other customizable trans-acting regulatory systems, such as CRISPR/Cas and sRNAs, will enable researchers to optimize any genetic system of interest.