Histone H2AX and DNA damage response machinery (H2AX/DDR)

Phosphorylated histone H2AX, commonly referred to as gamma-H2AX (γH2AX), is a variant of the H2A histone family that undergoes rapid phosphorylation at Serine 139 by PI3K-like kinases such as ATM, ATR, and DNA-PK in response to DNA double-strand breaks (DSBs) [PMID: 10359813]. This modification acts as a scaffold to recruit the DNA damage response (DDR) machinery, a complex network of proteins that sense, signal, and repair DNA lesions to maintain genomic integrity [PMID: 15467717]. The DDR machinery includes sensors (e.g., MRN complex), transducers (e.g., ATM, ATR), and effectors (e.g., p53, BRCA1, CHK1/2) that coordinate cell cycle arrest or apoptosis if the damage is irreparable [PMID: 21116281]. In oncology, the DDR pathway is a major therapeutic target; for instance, PARP inhibitors like Olaparib exploit "synthetic lethality" in BRCA-deficient cancers by blocking alternative repair pathways [PMID: 15831875]. γH2AX itself is widely utilized as a sensitive pharmacodynamic biomarker in clinical trials to quantify DNA damage induction and the efficacy of DDR-targeted agents [PMID: 23548214]. Therapeutic challenges include the development of resistance through secondary mutations and systemic toxicities such as myelosuppression due to the pathway's role in normal hematopoiesis [PMID: 28841415].

Other names

gamma-H2AXH2AFXgamma-H2A.XDNA damage response pathwayDDR machinery

Inhibition of specific DDR enzymes (e.g., PARP, ATM, ATR) to prevent DNA repair, often inducing synthetic lethality in cells with pre-existing repair deficiencies [PMID: 15831875, 28841415].