ATM recognizes H2AFX-Nucleosomes

H2AFX (also known as H2AX) is a variant of histone H2A and is present in a portion of nucleosomes. While H2AFX-containing nucleosomes (H2AFX-nucleosomes) are not specifically recruited to the sites of DNA double-strand breaks (DSBs), ATM recognizes the carboxyl tails of H2AFX on H2AFX-nucleosomes in the vicinity of DSBs as a suitable phosphorylation substrate. The phosphorylated H2AFX (gamma-H2AX) plays a crucial role in the retention of DNA repair proteins at DSBs, manifested in the formation of ionizing radiation-induced foci (Paull et al. 2000, Celeste et al. 2002, Redon et al. 2002, Celeste et al. 2003, Fernandez-Capetillo et al. 2004).

H2AFX（亦称H2AX）为组蛋白H2A的变异体，存在于核小体的一部分。尽管含有H2AFX的核小体（H2AFX-核小体）并非专门被招募至DNA双链断裂（DSBs）的位点，但ATM识别DSBs邻近的H2AFX-核小体上H2AFX的羧基尾作为适宜的磷酸化底物。磷酸化的H2AFX（γ-H2AX）在DNA修复蛋白在DSBs处的保留中扮演着至关重要的角色，这一作用体现在电离辐射诱导的焦点的形成上（Paull等人，2000年，Celeste等人，2002年，Redon等人，2002年，Celeste等人，2003年，Fernandez-Capetillo等人，2004年）。