Rational gRNA Design Based on Transcription Factor Binding Data

ABSTRACT

The CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 system has become a standard tool in many genome engineering endeavors. The endonuclease-deficient version of Cas9 (dCas9) is also a powerful programmable tool for gene regulation. In this study, we made use of Saccharomyces cerevisiae transcription factor binding data to obtain a better understanding of the interplay between transcription factor binding and binding of dCas9 fused to an activator domain, VPR. More specifically, we targeted dCas9-VPR towards binding sites of Gcr1-Gcr2 and Tye7 present in several promoters of genes encoding enzymes engaged in the central carbon metabolism. From our data, we observed an upregulation of gene expression when dCas9-VPR was targeted next to a transcription factor binding motif, whereas downregulation or no change was observed when dCas9 was bound on a transcription factor motif. This suggests a steric competition between dCas9 and the specific transcription factor. Integrating transcription factor binding data, therefore, proved to be useful for designing gRNAs for CRISPRi/a applications.