FIGURE 3.

Schematic representation showing that expression levels of SYCE2 in somatic cells define the steady‐state ATM activity by affecting heterochromatin protein 1α (HP1α) localization in the nuclear microenvironment. When the expression level of SYCE2 is low (left), HP1α is bound to the heterochromatin marker trimethylated histone H3 lysine 9 (H3K9me3), and the steady‐state ATM activity and DNA double‐strand break repair activity are kept low. When the expression level of SYCE2 is high (right), SYCE2 directly binds to HP1α and dissociates HP1α from H3K9me3, namely heterochromatin. As a result, HP1α will be distributed in euchromatin as well, which will potentiate the steady‐state ATM activity and increase the levels of total DNA double‐strand break repair activity following the induction of exogenous DNA damage