<p>In eukaryotic cells, DNA
is packaged into a structure named chromatin which contains DNA and proteins.
Nucleosomes are building blocks of chromatin and contain DNA wrapped around a
histone octamer. Chromatin modifications (histone post-translational modifications
and histone variants) play central roles in various cellular processes
including gene expression and DNA damage response. Chromatin modifying enzymes
use metabolites as co-substrates and co-factors, and changes in metabolic pathways
and metabolite availability affects chromatin modifications and
chromatin-associated functions. Moreover, recent studies have uncovered direct
roles of metabolic enzymes in chromatin-associated functions. Fumarase, a TCA
cycle enzyme that catalyzes the reversible conversion of fumarate to malate in
mitochondria (a hydration reaction), is an example of an enzyme with dual
functions in metabolism and genome integrity. Cytoplasmic fraction of yeast fumarase,
Fum1p, localizes to the nucleus and promotes growth upon DNA damage. Fum1p promotes
homologous recombination by enhancing DNA end resection. Human fumarase is
involved in DNA repair by non-homologous end joining. Here, we provide evidence
that yeast Fum1p and the histone variant Htz1p are also involved in DNA
replication stress response and DNA repair by non-homologous end joining (NHEJ).
Using mutants lacking the histone variant <i>HTZ1</i>, we show that high
cellular levels of fumarate, by deletion of <i>FUM1</i> or addition of
exogenous fumarate, suppressed the sensitivity to DNA replication stress by
modulation of activity of Jhd2p. This suppression required sensors and
mediators of the intra-S phase checkpoint, but not factors involved in the
processing of replication intermediates. These results imply that high cellular
levels of fumarate can confer resistance to DNA replication stress by bypassing
or complementing the defects caused by loss of <i>HTZ1</i> and replication fork
processing factors. We also show that upon induction of DSBs, exogenous
fumarate conferred resistance to mutants with defects in NHEJ, early steps of
homologous recombination (DNA end resection pathway) or late steps of
homologous recombination (strand invasion and exchange). Taken together, these
results link the metabolic enzyme fumarase and the metabolite fumarate to DNA
damage response and show that modulation of DNA damage response by regulating
activity of chromatin modifying enzymes is a plausible pathway linking
metabolism and nutrient availability to chromatin-associated functions like
genome integrity.<br><a></a></p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8047160 |
| Date | 10 June 2019 |
| Creators | Faeze Saatchi (5930213) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/INVESTIGATING_ROLES_OF_THE_METABOLIC_ENZYME_FUMARASE_AND_THE_METABOLITE_FUMARATE_IN_DNA_DAMAGE_RESPONSE/8047160 |
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