WSU faculty contributes to new study mapping the genetic architecture of the DNA damage response

Joshua Heyza, Ph.D., assistant professor in the Institute of Environmental Health Sciences and Department of Pharmacology at Wayne State University, contributed to a collaborative study published in Nature Biotechnology mapping relationships among DNA damage response genes and examining how the loss of one DNA repair pathway changes cells’ dependence on others.

Led by Alberto Ciccia, Ph.D., at Columbia University, the study used CRISPR–Cas12a technology to disrupt 233 DNA damage response genes individually and in more than 27,000 pairwise combinations. The researchers identified over 750 high-confidence genetic interactions, revealing connections between repair pathways and dependencies that emerge when specific repair proteins are lost. These findings provide a resource for understanding DNA repair and identifying potential vulnerabilities in cancers with DNA repair defects.

Heyza’s contribution builds on his imaging work in a 2023 study published in Science, which provided direct visual evidence that RHINO recruits DNA polymerase θ (Pol θ) to DNA double-strand breaks during mitosis to support repair through microhomology-mediated end joining.

In the current study, Heyza used CRISPR-based endogenous protein tagging and live-cell imaging to investigate a connection between the Fanconi anemia pathway and DNA repair during mitosis. He introduced a fluorescent tag into the endogenous RHNO1 gene, which encodes RHINO, in cells containing endogenously HaloTagged DNA Pol θ, enabling both repair proteins to be visualized in living cells.

Heyza’s imaging helped reveal that cells lacking FANCL, a component of the Fanconi anemia pathway, form more RHINO and Pol θ foci during mitosis, particularly when DNA replication stress is induced. These findings support a model in which GEN1 processes unresolved DNA structures into breaks that are then repaired through a mechanism involving RHINO and Pol θ.

The study reveals how defects in the Fanconi anemia pathway create a dependence on DNA repair during cell division, expanding understanding of how cells compensate when particular repair pathways fail.