# Control of Commitment Steps in Mammalian Homologous Recombination

> **NIH NIH R01** · RUTGERS, THE STATE UNIV OF N.J. · 2021 · $319,991

## Abstract

Project Summary: “Control of Commitment Steps in Mammalian Homologous Recombination”
The appearance of many cancer cases, especially breast, ovarian, and pancreatic cancer, is linked to problems
with DNA repair. Deficiencies in key DNA repair genes, such as BRCA1, PALB2 and BRCA2 , are associated
with inefficient DNA repair by the homologous recombination (HR) pathway. Each of these factors is required to
load the key HR intermediate, RAD51, at DNA double-strand break sites. The exact mechanism by which BRCA1
is recruited to DNA break sites and becomes activated at those break sites is not fully understood. HR efficiency
is also affected by the activity of certain regulators. 53BP1 regulates HR by reducing BRCA1-mediated loading
of RAD51. RNF4 is reported to regulate recruitment of BRCA1 to DNA breaks, and increased abundance of
RNF4 correlates with poor survival in breast cancer. The overall goal of this proposal is to clarify how BRCA1
becomes localized and activated at DNA breaks, and how interactions between BRCA1 and PALB2 mediate
productive HR. This goal will be realized by investigating three mechanisms that control recruitment of the
BRCA1-associated repair machinery. First, we will test how post-translational modification of proteins at break
sites by ubiquitination and SUMOylation affects BRCA1-mediated HR. In particular, we will focus on RNF4, a
‘SUMO-targeted E3 ubiquitin ligase’ with a known role in DNA repair, which appears to affect the growth of
cancer cells. Using a conditional-knockout mouse model that was recently generated by our lab, we will test how
RNF4-mediated ubiquitination affects turnover of repair components at DNA breaks, and how this affects cell
survival after DNA damage. Secondly, we will test the contributions of two factors that appear to be important for
recruitment of BRCA1 to DNA damage sites. These factors are BARD1, a RING domain-containing protein that
interacts constitutively with BRCA1; and TOPBP1, a large scaffold protein that loads onto chromatin at DNA
damage sites and recruits multiple DNA repair factors. Data obtained in our lab using genetically-modified mouse
models and mass spectrometry supports a role for BARD1 and TOPBP1 in BRCA1 recruitment, and this project
will address how important they are for BRCA1-mediated HR. The third part of the proposal focuses on
interactions between BRCA1 and PALB2. BRCA1 is able to form a complex with PALB2 by association of helical
elements in both proteins to form a ‘coiled coil’ domain. The heterodimer of BRCA1:PALB2 stabilizes BRCA2 at
the break site, which in turn helps load RAD51 to facilitate HR. PALB2 can also form a coiled coil by
homodimerization, however, which prevents it from interacting with BRCA1 and limits the efficiency of HR. The
ability of PALB2 to form non-recombinogenic and pro-recombinogenic complexes is proposed to regulate HR
efficiency, hence we have studied the different complexes in detail using NMR spectroscopy. By studying and
testing ...

## Key facts

- **NIH application ID:** 10120766
- **Project number:** 2R01CA190858-06A1
- **Recipient organization:** RUTGERS, THE STATE UNIV OF N.J.
- **Principal Investigator:** Samuel Bunting
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $319,991
- **Award type:** 2
- **Project period:** 2021-02-01 → 2021-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10120766

## Citation

> US National Institutes of Health, RePORTER application 10120766, Control of Commitment Steps in Mammalian Homologous Recombination (2R01CA190858-06A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10120766. Licensed CC0.

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