DNA repair nuclease/redox regulator APEX1

APEX1 is a multifunctional 35.5 kDa protein that plays dual roles in cellular DNA repair and redox regulation (UniProt: P27695). As an apurinic/apyrimidinic endonuclease, it initiates base excision repair of oxidative DNA lesions by catalyzing phosphodiester backbone cleavage. Beyond DNA repair, APEX1 regulates transcriptional factors through reversible redox modification of their DNA-binding domains, exemplified by the FOS/JUN AP-1 complex, thereby controlling cellular responses to oxidative stress.

APEX1 operates primarily in the nucleus where it coordinates multiple DNA maintenance pathways, including immunoglobulin class switch recombination and mRNA turnover regulation via MYC control (UniProt: P27695). The protein also associates with ribosomal RNA quality control processes. UniProt records no inherent disease associations in its curated disease database.

APEX1 is upregulated in Alzheimer's Disease brain tissue. Chaparral AD proteomics data from post-mortem AD brain versus age-matched controls show increased APEX1 levels with a mean log2 fold-change of 1.29 across subcellular fractions (Chaparral AD proteomics). This elevation suggests enhanced oxidative stress response and DNA repair activation in AD pathology, potentially reflecting the accumulation of oxidative damage characteristic of neurodegeneration.