Cloning and structural analysis of mouse Apex gene encoding the major apurinic/apyrimidinic endonuclease

The APEX nuclease is a mammalian multifunctional repair enzyme having 5' apurinic/apyrimidinic (AP) endonuclease, DNA 3' repair diesterase, 3'-5' exonuclease and DNA 3' phosphatase activities. The mouse Apex gene for the enzyme, was isolated from a mouse leukocyte genomic library by plaque hybridization with the mouse Apex cDNA as a probe. The nucleotide sequence of the Apex gene and its 5'-and 3'-flanking regions were determined. With reference to the published Apex cDNA sequence, the mouse Apex gene can be divided into five exons and four introns with a total length of about 2.6 kb. The boundaries between exon and intron follow the GT/AG rule. The translation initiation and termination sites are located in exons Ⅱ and Ⅴ, respectively. A part of the 5' flanking region belongs to a CpG island, which extends to intron Ⅱ. The CpG island is thought to be a putative transcription regulatory region of the Apex gene, a housekeeping gene.

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