APEX2(redirected from APEX nuclease (apurinic/apyrimidinic endonuclease) 2)
APEX2A gene on chromosome Xp11.21 that encodes a weak apurinic/apyrimidinic (AP endoDNAase), which is involved in the DNA base excision repair (BER) pathway of DNA lesions induced by oxidative and alkylating agents, and in the redox regulation of transcription factors. APEX2 has robust 3'-5' exonuclease activity on 3'-recessed heteroduplex DNA, and preferentially removes mismatched nucleotides; it also has robust 3'-phosphodiesterase-induced removal of 3'-damaged termini formed in DNA by oxidative agents. It is required for somatic hypermutation (SHM) and DNA cleavage step of class-switch recombination of immunoglobulin genes, as well as for proper cell cycle progression during proliferation of peripheral lymphocytes.
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