# Replication fork dynamics and repair by Rad51 paralogs after DNA alkylation

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2021 · $372,608

## Abstract

7. Project Summary
Misrepair of DNA damage is a hallmark of cancer. We discovered that the budding yeast Shu complex is a
conserved regulator of DNA repair through a central role in Rad51 regulation. Rad51 functions during the high
fidelity homologous recombination pathway to find and invade a homologous template for repair and also
during replication fork protection and restart. Rad51 is tightly regulated in cells by accessory proteins,
collectively called the Rad51 mediators, including the Shu complex. In humans, misregulation of hRAD51 or
its mediators is associated with cancer predisposition (particularly breast and ovarian cancers) and Fanconi
anemia, which is also characterized by anemia and cancer. We found that disruption of the yeast Shu complex
leads to cellular death specifically upon exposure to alkylation induced DNA damage. Alkylation damage is
caused by a myriad of industrial and consumer-based sources and is pervasive in our environment. DNA
alkylation leads to replication stress and DNA damage. If DNA is alkylated during replication, then the
replication fork can stall or collapse, and many repair mechanisms can be utilized to tolerate, bypass, or repair
the damaged DNA. How a cell commits to a specific repair pathway is largely known. In budding yeast, the
Shu complex is critical in the processing of replication forks damaged by alkylating agents. This complex is
highly conserved throughout eukaryotes and contains the Rad51 paralogs, proteins that are structurally similar
to the central DNA repair protein Rad51 and are mutated in cancer. In this study, we aim to elucidate the role
of the yeast and human Shu complexes in repair of DNA alkylation damage at a replication fork. We are
testing the hypothesis that the Shu complex is a critical key regulator of DNA damage tolerance at a replication
fork by specifically recognizing alkylation induced DNA damage to promote Rad51-mediated template switch
and protect forks from double-strand break induction by AP endonucleases. Using what we learn in yeast to
quickly and efficiently identify key substrates, residues, and protein targets, we will expand our studies into
human cell lines where we will investigate the role of the human Shu complex in tolerance of alkylation
damage. In addition, we will identify at risk individuals harboring mutations in these important genes that may
be more sensitive to DNA alkylation damage and therefore susceptible to cancer. Collectively, these studies
will provide key insights into the role of the Shu complex in tolerance of DNA alkylation damage and elucidate
how this complex promotes error-free DNA repair to prevent genetic instability and cancer.
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## Key facts

- **NIH application ID:** 10162586
- **Project number:** 5R01ES030335-03
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Kara A Bernstein
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $372,608
- **Award type:** 5
- **Project period:** 2019-09-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10162586

## Citation

> US National Institutes of Health, RePORTER application 10162586, Replication fork dynamics and repair by Rad51 paralogs after DNA alkylation (5R01ES030335-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10162586. Licensed CC0.

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