A dynamic subpopulation of CRISPR-Cas overexpressers allows Streptococcus pyogenes to rapidly respond to phage [RNA-seq]

Cas9 is a transcriptional autoregulator in many strains of S. pyogenes. A natural single guide RNA (tracr-L) directs Cas9 to bind to and repress its promoter. In this study, we aimed to determine whether tracr-L, crRNAs, or other noncanonical guide RNAs direct Cas9 to bind to other regions of the genome and potentially regulate the expression of additional genes. To determine whether CRISPR-Cas overexpression or loss leads to changes in gene expression, we generated strains of S. pyogenes that overexpress (∆tracr-L) or lack (∆CRISPR-Cas) the CRISPR-Cas system and performed RNA-Seq along with the WT strain.