Mediator of DNA damage checkpoint protein 1 (MDC1)

Mediator of DNA damage checkpoint protein 1 (MDC1) is a large nuclear scaffold/adaptor protein essential for cellular responses to DNA double-strand breaks. It contains an N-terminal forkhead-associated (FHA) domain, two BRCA1 C-terminal (BRCT) motifs, and a central tandem repeat region. MDC1 directly binds phosphorylated histone H2AX (γH2AX) at sites of DNA damage, assembling and retaining DNA damage response (DDR) and repair proteins, and is critical for activation of the intra-S phase and G2/M cell cycle checkpoints. It coordinates downstream recruitment and activation of kinases like ATM, CHEK1, and CHEK2 and helps stabilize and regulate p53 activity. Loss or dysfunction of MDC1 causes radiosensitivity, impaired DNA damage checkpoints, defects in homologous recombination, and tumor susceptibility[2][4][6]. There are no current therapies directly targeting MDC1, but its role in DNA repair makes it a potential biomarker and research target for cancer and other genomic instability disorders.

Other names

Nuclear factor with BRCT domains 1 (NFBD1)KIAA0170Em:AB023051.5

Not applicable; no direct drugs currently approved. Mechanistically, targeting MDC1 would likely modulate DNA repair and checkpoint response pathways.