Epigenetic instability due to defective replication of structured DNA

Area of Science:

• Epigenetics
• DNA Replication
• Chromatin Biology

Background:

• Accurate propagation of histone marks during DNA replication is essential for maintaining cellular identity.
• Parental histone recycling to daughter strands is thought to be tightly coupled with replication.
• The role of DNA translesion synthesis factors in chromatin maintenance is not fully understood.

Purpose of the Study:

• To investigate the role of REV1 in maintaining repressive chromatin marks and gene silencing.
• To explore the requirement of REV1 in the replication of G-quadruplex (G4) forming DNA sequences.
• To elucidate the mechanism by which REV1 influences chromatin states at G4 structures.

Main Methods:

• Utilized the avian cell line DT40.
• Assessed the impact of REV1 deficiency on chromatin marks and gene silencing.
• Investigated DNA replication dynamics at G4 forming sequences.
• Performed locus-specific G4 sequence transplantation experiments.

Main Results:

• REV1 is required for maintaining repressive chromatin marks and gene silencing near G4 structures.
• REV1 plays a previously unappreciated role in the replication of G4 forming sequences.
• Loss of REV1 leads to derepression of a silent locus when a G4 sequence is introduced.
• REV1 deficiency results in uncoupling of DNA synthesis from histone recycling at G4 DNA.

Conclusions:

• REV1 is essential for processive DNA replication at G4 DNA structures.
• Failure in G4 replication in REV1-deficient cells leads to biased histone incorporation and loss of repressive chromatin.
• REV1 acts as a key regulator linking DNA replication fidelity at G4s to epigenetic maintenance.