# Genome‐Wide Analysis of DtxR and HrrA Regulons Reveals Novel Targets and a High Level of Interconnectivity Between Iron and Heme Regulatory Networks in Corynebacterium glutamicum

## TL;DR

This study explores how two key regulators, DtxR and HrrA, control iron and heme balance in Corynebacterium glutamicum, revealing new targets and showing how these systems are closely linked.

## Contribution

The first genome-wide analysis of DtxR and HrrA binding under varying iron and heme conditions in C. glutamicum.

## Key findings

- 25 novel DtxR targets and 210 previously unrecognized HrrA targets were identified.
- Shared targets between DtxR and HrrA highlight interconnected regulatory networks.
- Weak ChAP-Seq peaks were shown to significantly impact gene expression.

## Abstract

Iron is vital for most organisms, serving as a cofactor in enzymes, regulatory proteins, and respiratory cytochromes. In
Corynebacterium glutamicum
, iron and heme homeostasis are tightly interconnected and controlled by the global regulators DtxR and HrrA. While DtxR senses intracellular Fe2+, HrrSA is activated by heme. This study provides the first genome‐wide analysis of DtxR and HrrA binding dynamics under varying iron and heme conditions using chromatin affinity purification and sequencing (ChAP‐Seq). We revealed 25 novel DtxR targets and 210 previously unrecognized HrrA targets. Among these, metH, encoding homocysteine methyltransferase, and xerC, encoding a tyrosine recombinase, were bound by DtxR exclusively under heme conditions, underscoring condition‐dependent variation. Activation of metH by DtxR links iron metabolism to methionine synthesis, potentially relevant for the mitigation of oxidative stress. Beyond novel targets, 16 shared targets between DtxR and HrrA, some with overlapping operator sequences, highlight their interconnected regulons. Strikingly, we demonstrate the significance of weak ChAP‐Seq peaks that are often disregarded in global approaches, but feature an impact of the regulator on differential gene expression. These findings emphasize the importance of genome‐wide profiling under different conditions to uncover novel targets and shed light on the complexity and dynamic nature of bacterial regulatory networks.

Iron is essential for life, yet excessive levels can quickly lead to cellular damage via oxidative stress, underscoring the need for global regulators of iron and heme homeostasis. In this study, we present a genome‐wide analysis of the binding patterns of DtxR and HrrA in
Corynebacterium glutamicum
. Our findings highlight the interconnected nature of DtxR and HrrA networks and underscore the value of condition‐specific analyses for a deeper understanding of bacterial adaptation to environmental changes.