Dynamic regulation of histone modification
is critical to many cellular processes includ‑
ing DNA repair where changes in chromatin
architecture are thought to enhance the acces‑
sibility of DNA repair factors to damaged
DNA. In this issue of Nature Cell Biology, Jiang
et al. show that fumarase, an enzyme normally
associated with oxidative metabolism in the
mitochondria, is recruited to chromatin to
facilitate DNA repair, revealing a role for this
metabolic enzyme in the regulation of both
histone methylation and DNA double strand
break (DSB) repair 1 .
DSBs are considered the most cytotoxic form
of DNA damage. They occur endogenously and
are produced by exposure to ionizing radia‑
tion (IR) and many chemotherapeutic agents.
Understanding how DSBs are detected and
repaired may therefore be critical for cancer
prevention, for improving patient responses
to radiation‑ and chemotherapy and for miti‑
gating the toxic effects of cancer treatment on
normal tissues 2 . In mammalian cells, one of
the main pathways for the repair of IR‑induced
DSBs is non‑homologous end joining (NHEJ).
In NHEJ, IR‑induced DSBs are detected by the
Ku70/80 heterodimer (Ku), which recruits
other NHEJ factors, including the DNA‑
dependent protein kinase catalytic subunit
(DNA‑PKcs) to the break to facilitate repair
by the XRCC4–XLF–DNA ligase 4 complex 3 .