PROJECT SUMMARY/ABSTRACT
Exposure to environmental agents including heavy metals, air pollutants, pesticides and
radiation induces the formation of aberrant RNA-DNA hybrids termed R-loops. Unresolved R-
loops are the cause of DNA damage and genome instability, and are also seen in
neurodegenerative diseases, e.g. amyotrophic lateral sclerosis (ALS), frontotemporal dementia
(FTD), fragile X syndrome, and Friedreich's ataxia. The elimination of these pathological RNA-
DNA hybrids is dependent on the Fanconi anemia (FA) pathway of DNA damage response and
on the tumor suppressors BRCA1 and BRCA2. Recent studies have also implicated several
nucleic acid motor proteins, namely, FANCM, Senataxin (SETX), and Aquarius (AQR), in R-loop
resolution. AQR is the least understood among these motor proteins and the mechanism by
which AQR helps resolve R-loops remains elusive.
We hypothesize that AQR engages and dissociates R-loop structures to prevent their
accumulation in cells. In this project, we will apply our considerable expertise in molecular
studies of nucleic acid motor proteins to define the mechanism by which AQR functions in the
R-loop resolution and genome preservation. In Aim 1, we will purify AQR, investigate its
association with R-loop structures, and test its ability to dissociate these structures. Mutants of
AQR defective in nucleic acid binding or ATP hydrolysis will be generated to establish the
relevance of these attributes in vitro and in cells. In Aim 2, we will identify cofactors of AQR,
purify them, and define their influence on AQR's activity in R-loop dissociation in reconstituted
biochemical systems and in cells. The results from our project will shed light on a poorly
understood pathway of genome preservation and are expected to contribute toward the
development of novel strategies to avoid the accumulation of R-loops upon exposure to
environmental stress and mutagens, and to treat human diseases including neurodegeneration
and cancer.