BAHCC1 binds H4K20me1 to facilitate the MCM complex loading and DNA replication

Area of Science:

• Epigenetics and chromatin biology
• Molecular mechanisms of DNA replication
• Cell cycle regulation

Background:

• Histone modifications, such as mono-methylation of histone H4 lysine 20 (H4K20me1), play critical roles in regulating fundamental cellular processes.
• The precise mechanisms by which H4K20me1 influences DNA replication, cell cycle progression, and DNA damage repair are not fully understood.

Purpose of the Study:

• To elucidate the role of the BAHCC1 tandem Tudor domain (BAHCC1^TTD) in recognizing H4K20me1.
• To investigate how BAHCC1^TTD-mediated H4K20me1 recognition facilitates DNA replication origin activation and overall DNA replication.

Main Methods:

• Biochemical assays to assess protein-protein interactions and binding specificity.
• Structural biology to determine the interaction interface between BAHCC1^TTD and H4K20me1.
• Genomic analyses to map recruitment sites and assess genome-wide effects.
• Cellular experiments to evaluate the impact of BAHCC1 depletion or BAHCC1^TTD:H4K20me1 interaction disruption on DNA replication and cell cycle progression.

Main Results:

• BAHCC1^TTD selectively binds to H4K20me1, distinguishing it from other methylation states.
• BAHCC1^TTD facilitates the recruitment of BAHCC1 and the Mini-chromosome Maintenance (MCM) complex to replication origins.
• The interaction between BAHCC1^TTD and H4K20me1, alongside the Origin Recognition Complex (ORC) reading H4K20me2, is essential for MCM loading and replication origin activation.
• Depletion of BAHCC1 or disruption of the BAHCC1^TTD:H4K20me1 interaction impairs MCM loading, leading to replication defects and cell cycle progression issues.

Conclusions:

• BAHCC1^TTD acts as a key effector that translates H4K20me1 signals into the recruitment of the MCM complex.
• This mechanism is vital for efficient DNA replication origin activation and subsequent cell cycle progression.
• The study reveals a novel epigenetic regulatory pathway controlling DNA replication initiation through specific histone mark recognition.