CRISPathBrick: Modular Combinatorial Assembly of Type II-A CRISPR Arrays for dCas9-Mediated Multiplex Transcriptional Repression in <i>E. coli</i>

TLDR

Programmable control of a global regulator would enable simultaneous repression of multiple genes, and although CRISPR/Cas systems can be engineered for sequence‑specific transcriptional repression, only a few applications have been reported. This study develops a CRISPathBrick vector that allows rapid modular assembly of natural type II‑A CRISPR arrays to simultaneously repress multiple target genes in *E. coli*. The vector incorporates an iterative spacer‑insertion scheme that builds combinatorial arrays from few DNA parts, and a pCRISPReporter plasmid quantifies dCas9‑mediated repression from endogenous promoters.

Abstract

Programmable control over an addressable global regulator would enable simultaneous repression of multiple genes and would have tremendous impact on the field of synthetic biology. It has recently been established that CRISPR/Cas systems can be engineered to repress gene transcription at nearly any desired location in a sequence-specific manner, but there remain only a handful of applications described to date. In this work, we report development of a vector possessing a CRISPathBrick feature, enabling rapid modular assembly of natural type II-A CRISPR arrays capable of simultaneously repressing multiple target genes in Escherichia coli. Iterative incorporation of spacers into this CRISPathBrick feature facilitates the combinatorial construction of arrays, from a small number of DNA parts, which can be utilized to generate a suite of complex phenotypes corresponding to an encoded genetic program. We show that CRISPathBrick can be used to tune expression of plasmid-based genes and repress chromosomal targets in probiotic, virulent, and commonly engineered E. coli strains. Furthermore, we describe development of pCRISPReporter, a fluorescent reporter plasmid utilized to quantify dCas9-mediated repression from endogenous promoters. Finally, we demonstrate that dCas9-mediated repression can be harnessed to assess the effect of downregulating both novel and computationally predicted metabolic engineering targets, improving the yield of a heterologous phytochemical through repression of endogenous genes. These tools provide a platform for rapid evaluation of multiplex metabolic engineering interventions.