Dbf4-dependent kinase finetunes Ino80 function at chromosome replication origins

Area of Science:

• Molecular Biology
• Cell Cycle Regulation
• Chromatin Dynamics

Background:

• The Dbf4-Dependent Kinase (DDK) is crucial for S phase progression.
• DDK phosphorylates the minichromosome maintenance (MCM) complex to initiate DNA replication.
• Limited knowledge exists regarding other DDK substrates and functions.

Purpose of the Study:

• To identify novel nuclear DDK targets and understand their roles.
• To investigate the impact of DDK phosphorylation on chromatin remodeling complexes.

Main Methods:

• Utilized a two-pronged mass spectrometry approach.
• Analyzed the nuclear phosphoproteome to identify DDK-dependent phosphorylation sites.

Main Results:

• Identified approximately 400 DDK-dependent phosphorylation targets.
• Discovered Arp8, a subunit of the INO80 chromatin remodeling complex, as a novel DDK target.
• Arp8 phosphorylation stabilizes the INO80 complex and optimizes nucleosome spacing at replication origins.

Conclusions:

• DDK regulates chromatin remodeling complexes, specifically the INO80 complex via Arp8 phosphorylation.
• This regulation fine-tunes chromatin architecture to facilitate DNA replication and enhance the replication stress response.
• DDK controls both core replication machinery and factors establishing replication-permissive chromatin states.