HdaB: a novel and conserved DnaA-related protein that targets the RIDA process to stimulate replication initiation

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• Precise control of bacterial DNA replication initiation by the DnaA initiator is crucial for cell cycle coordination.
• The Hda/HdaA protein regulates DnaA activity via Regulatory Inactivation of DnaA (RIDA) to prevent over-initiation, a process that also targets DnaA for proteolysis in Caulobacter crescentus.

Purpose of the Study:

• To investigate the role of the RIDA process in bacterial adaptation to environmental changes.
• To identify and characterize novel proteins involved in DnaA regulation.

Main Methods:

• Identification of a novel DnaA-related protein, HdaB.
• In vivo interaction studies between HdaB and HdaA.
• Expression analysis of HdaB during different growth phases.
• Phenotypic analysis of HdaB expression in C. crescentus.

Main Results:

• HdaB homologs inhibit the RIDA process, causing over-initiation and cell death when expressed in growing cells.
• HdaB interacts with HdaA, likely by sequestering it away from DnaA.
• HdaB accumulates during stationary phase and accelerates replication restart after exiting this phase.

Conclusions:

• HdaB acts as a key regulator of DNA replication restart following stationary phase.
• HdaB accumulation during stationary phase prepares Alphaproteobacteria for rapid growth resumption in fluctuating environments.
• This mechanism is vital for free-living and facultative intracellular Alphaproteobacteria adapting to changing conditions.