Scientists at the Tokyo University of Science led by Prof. Sachihiro
Matsunaga have identified a novel epigenetic regulation mechanism that is
involved in DNA damage repair in plants. At the center of the mechanism is a
histone demethylase enzyme called lysine-specific demethylase 1-like 1
(LDL1), which according to Professor Matsunaga has a lot of real-world
applications.

Various stresses cause instabilities or errors in an organism's genome,
resulting to damages or "breaks" in the sequences. These breaks are repaired
autonomously by a process called homologous recombination (HR). HR is then
essential for maintaining a genome's stability. The chromatin structure
needs to be modified for HR to occur smoothly. Professor Matsunaga's
previously discovered protein called RAD54 was found to be involved in
chromatin remodeling in Arabidopsis, helping genomic stability and response
to DNA damage. However, recruitment of RAD54 at the site of HR and the
proper dissociation of RAD54 from the site are important for it to be
effective.

The scientists identified and shortlisted proteins that interact with RAD54
and regulate its dynamics with chromatin during HR-based DNA damage repair
in Arabidopsis. They then identified, for the first time, that the histone
demethylase LDL1 interacts with RAD54 at DNA damage sites. They found that
RAD54 specifically interacts with the methylated 4th lysine amino acid on
one of the four core histones in the chromatin, H3 (H3K4me2). The scientists
then found that LDL1 suppresses this interaction by demethylating H3K4me2.
They concluded that LDL1 removes excess of RAD54 from DNA damage sites via
the demethylation of H3K4me2 and thus promotes HR repair in Arabidopsis.
Thus, LDL1 ensures proper dissociation of RAD54 from the HR repair site in
the DNA.

Professor Matsunaga explains the most important part of their research.
"Plants can be treated with LDL1 to artificially control epigenetic
modification so that they become more tolerant to stresses such as
infections, environmental stresses and mechanical stress. This will be
useful in creating resistant varieties of crops with improved growth and
longevity and better characteristics, thus contributing to global food
security."



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