Myc-driven chromatin accessibility regulates Cdc45 assembly into CMG helicases

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Myc is a transcription factor implicated in tumorigenesis.
• Myc's role in DNA replication initiation is not fully understood.
• Over-activation of replication origins contributes to cancer development.

Purpose of the Study:

• To elucidate the non-transcriptional mechanism of Myc in activating DNA replication origins.
• To investigate the role of Myc-Box II in Myc-driven replication.
• To identify key protein interactions facilitating Myc's function in replication.

Main Methods:

• Chromatin immunoprecipitation assays to assess protein binding and chromatin accessibility.
• Analysis of replication origin firing using molecular biology techniques.
• Investigating protein-protein interactions between Myc, CMG components, and co-factors.
• Functional assays using Myc mutants and co-expression systems.

Main Results:

• Myc directly activates the Cdc45-MCM-GINS (CMG) helicase at replication origins.
• Myc induces chromatin decondensation and facilitates CMG complex assembly.
• Myc-Box II is essential for Myc-mediated chromatin accessibility, CMG recruitment, and replication stimulation.
• Interactions with GCN5, Tip60, and TRRAP are crucial for Myc-induced chromatin unfolding and Cdc45 recruitment.
• Myc and Cdc45 directly interact, and their functional cooperation is vital for CMG assembly and DNA replication.

Conclusions:

• Myc plays a direct, non-transcriptional role in activating DNA replication origins via CMG helicase activation.
• Myc-Box II and interactions with co-factors like GCN5 are critical for Myc's function in replication initiation.
• Understanding this mechanism provides insights into Myc-driven tumorigenesis and potential therapeutic targets.