Elucidating the CodY regulon in Staphylococcus aureus USA300 lineage using ChIPexo

CodY is a conserved broad acting transcriptional factor that regulates the expression of genes related to amino acid metabolism and virulence in Staphylococcus aureus. CodY target genes have been studied by using in vitro DNA affinity purification and deep sequencing (IDAP-Seq). In this study we performed the first in vivo determination of CodY target genes using a novel CodY monoclonal antibody in established ChIP-exo protocols. Our results showed, 1) The same 165 CodY target genes in both strains; 2) That the differential binding intensity for the same target genes under the same conditions were due to sequence differences in the same CodY binding site in the two strains; 3) Based on transcriptomic data, a CodY regulon comprising 72 target genes that revealed that CodY is mainly involved in amino acid transport and metabolism, inorganic ion transport and metabolism, and cellular transcription and translation; and 4) CodY systematically regulated central metabolic flux to generate branched-chain amino acids (BCAAs) by mapping the CodY regulon onto a genome-scale metabolic model of S. aureus. Our study performed the first system-level analysis of CodY in two closely related dominant USA300 TCH1516 and LAC strains, thus expanding the size of the known CodY regulon, and giving new insights into the similarities and differences of CodY regulatory roles between closely related strains. Overall design: Expression profiling data for wild type S. aureus JE2 and its corresponding codY mutant strains were generated by RNA-seq, in duplicate