# Regulation of mitotic genome stability in yeast.

> **NIH NIH R35** · DUKE UNIVERSITY · 2021 · $591,231

## Abstract

A low level of genetic instability is required for adaptation and evolution, but such instability is also a potent driver
of human disease. Research in my lab focuses on genetic identification and molecular characterization of
processes that contribute to mitotic genome instability as well as DNA repair processes that promote genome
stability. The proposed research will primarily use budding yeast (Saccharomyces cerevisiae) as a model to
explore the repair of DNA strand breaks and how this impacts genome integrity. Double-strand breaks (DSBs)
are among the most detrimental of DNA lesions and are repaired either by homologous recombination (HR),
which uses an intact duplex as a repair template, or by nonhomologous end joining (NHEJ), which directly rejoins
broken ends. Although both are inherently high-fidelity processes, HR can result in loss of heterozygosity or can
engage dispersed repeated sequences to generate genome rearrangements. In the case of NHEJ, end
processing prior to ligation produces small-scale changes at the junction while joining the ends of different DSBs
generates genome rearrangements. Endonuclease-generated DSBs that have different end polarities will be
used to initiate HR between sequence-diverged substrates on different chromosomes. Comparative analyses of
HR product types and their strand compositions will reveal how end structure affects mitotic HR intermediates
and mechansims. The effects of large sequence discontinuities at the site of an initiating DSB will be examined.
In addition to use of sequence-specific enzymes to create targeted DSBs, topoisomerases break and rejoin DNA
strands to resolve topological problems that arise during transcription and replication. These enzymes form a
covalent link with one end of a nick; stabilization of cleavage intermediates with chemotherapeutic drugs leads
to persistent breaks that are highly toxic. We previously described a short-deletion signature of Top1 (a type I
enzyme that nicks one DNA strand) and defined the associated molecular mechanism. We recently discovered
that Top2 (a type II enzyme that nicks both strands to create a DSB) initiates the formation of de novo duplications
through the NHEJ pathway. We will examine how the mechanism of protein removal from DNA ends and how
the presence of ribonucleotides embedded in DNA affect Top2-dependent mutagenesis. Similar duplications are
found in tumor cells with a mutant form of TOP2a, and this mutant protein will be modeled in yeast. Building on
our long-term interests in recombination and mutagenesis in the budding yeast experimental system, we recently
expanded studies to include mutagenesis in the human fungal pathogen Cryptococcus deneoformans.
Cryptococcus must rapidly adapt to hostile conditions when it transitions from the environment to the human
host, and heat tolerance is critical for pathogenesis. Using a forward mutation assay, we found that a temperature
shift mimicking the environment-human transition is associ...

## Key facts

- **NIH application ID:** 10205748
- **Project number:** 2R35GM118077-06
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** SUE JINKS-ROBERTSON
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $591,231
- **Award type:** 2
- **Project period:** 2016-05-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10205748

## Citation

> US National Institutes of Health, RePORTER application 10205748, Regulation of mitotic genome stability in yeast. (2R35GM118077-06). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10205748. Licensed CC0.

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