DNMT3A Harboring Leukemia-Associated Mutations Directs Sensitivity to DNA Damage at Replication Forks

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Recurrent DNA methyltransferase 3A (DNMT3A) mutations are linked to chemoresistance and poor prognosis in acute myeloid leukemia (AML), particularly in older patients.
• Gene-expression studies suggest DNMT3A-mutated cells have impaired DNA damage response and replication fork integrity, indicating potential sensitivity to replication stress.

Purpose of the Study:

• To investigate whether pharmacologically induced replication fork stalling, using cytarabine, represents a therapeutic vulnerability in AML cells with DNMT3A(R882) mutations.

Main Methods:

• Utilized leukemia cell lines, genetic mouse models, and isogenic cells (with and without DNMT3A mutations) to assess sensitivity to cytarabine in vitro and in vivo.
• Analyzed DNA damage, signaling pathways, replication restart, and cell-cycle progression post-treatment and drug removal.
• Performed transcriptome profiling to identify pathways dysregulated by DNMT3A mutations.

Main Results:

• Cells with DNMT3A(R882) mutations exhibited increased sensitivity to replication stress, characterized by persistent intra-S-phase checkpoint activation and impaired DNA damage resolution.
• Higher rates of replication fork collapse were observed in DNMT3A-mutated cells after cytarabine washout.
• RNA sequencing revealed deregulation in cell-cycle progression, p53 activation, splicing, ribosome biogenesis, and metabolism.

Conclusions:

• DNMT3A mutations lead to a defect in recovering from replication fork arrest, causing accumulation of unresolved DNA damage with potential therapeutic tractability.
• DNMT3A plays a role in maintaining genome integrity during replication stress, beyond its epigenetic regulatory functions.