Mechanisms of genome damage and defense.

Two replication forks meet during termination to finish copying the DNA between them. We study how vertebrate cells complete this step accurately, including how topoisomerases relieve the topological stress that can prevent forks from converging.

Our work separates the challenge of termination into a topology problem involving TOP3α and a fork-stalling problem involving MCM10 and RTEL1. Biochemical assays and proteomics allow us to identify the proteins that act when normal termination is disrupted.

DNA damage can stall the polymerases that synthesize DNA while the replicative helicase continues unwinding. This separation of unwinding from synthesis, called uncoupling, can trigger degradation of newly synthesized DNA and reversal of the replication fork.

We use biochemical assays, supported by experiments in human cells, to determine how these responses begin and how the participating proteins control them. Our working model links uncoupling to nascent DNA degradation, checkpoint activation, fork slowing and reversal.

When a replication fork encounters a single-strand break, it can form a double-strand break and stop copying DNA. Repair must then complete DNA synthesis. We investigate the molecular events that connect fork breakage to repair and the sequence changes that repair leaves behind.

Our working model proposes that broken-fork processing produces precise deletions and, less frequently, templated insertions. The accompanying experiments measure these outcomes in a DNA substrate containing repeated tetO sequences.

Telomeres contain repeated DNA sequences bound by the Shelterin complex. Together, these components protect chromosome ends from being treated as DNA damage. Replication must copy this specialized structure while preserving chromosome-end protection.

We study how sequence loss is limited during telomere replication and which features of short telomeres determine whether they remain functional. Our biochemical approach allows us to test how individual components of telomere protection affect replication.