CLONING, SEQUENCE-ANALYSIS, AND CHROMOSOMAL ASSIGNMENT OF THE MOUSE APEX GENE

APEX nuclease (Apex gene product) is a mammalian multifunctional DNA r epair enzyme possibly involved in the repair of apurinic/apyrimidinic (AP) sites and single-strand DNA breaks with 3' termini blocked by nuc leotide fragments and also in transcriptional regulation via redox act ivation of the AP-1 transcription factors. We cloned a 15-kb DNA fragm ent containing the Apex gene from a mouse leukocyte genomic library an d determined a 4-kb stretch of its nucleotide sequence, including the complete sequence of the mouse Apex gene. The gene consists of 5 exons and 4 introns spanning 2.21 kb, and the boundaries between exons and introns follow the GT/AG rule. Two major and one minor transcription i nitiation sites were assigned to positions +1 and +24 and position +14 , respectively, by a combination of ribonuclease protection, primer ex tension, and 5' RACE analyses. Position +1 is located 312 nucleotides upstream from the ATG initiation codon. The translation initiation and termination sites are located in exon II and exon V, respectively. Th e sequenced 5' flanking region (1.32 kb) lacks a typical TATA box, but contains a CAAT box and putative binding sites for several transcript ion factors, such as ATF, NF-IL6, Sp1, and AP2. The 0.8-kb region from position -410 (5' flanking region) to position +386 (intron II) conta ins a CpG island. The Apex gene locus was mapped to mouse chromosome 1 4C2-D1 using in situ hybridization. (C) 1995 Academic Press, Inc.