FIG. 2.

The zebra fish genome has two copies of the APEX1 gene and two species of mRNA. (A) Diagram of zfAPEX1a and zfAPEX1b. Two copies of zfAPEX1 were identified by genomic PCR, followed by sequencing of the genes. zfAPEX1a contains introns and an extended 3′UTR, whereas zfAPEX1b lacks introns and the 3′ terminus of the 3′UTR. The coding sequence is identical. (B) Southern blot analysis of zebra fish genomic DNA confirms the presence of two copies of zfAPEX1. DNA extracted from adult fish was treated with NdeI (lane 1), NdeI and EcoRV (lane 2), or HindIII (lane 3) and resolved by agarose gel electrophoresis by means of a 1.5% gel. After blotting and denaturation, the membrane was probed with full-length cDNA. The diagram to the right shows the location of the NdeI, EcoRV, and HindIII sites in APEX1a. Note that APEX1b has no EcoRV or HindIII sites. (C) Diagram showing the alignment of the two mRNA species for ZAP1. mRNA species were obtained by RT-PCR as described in Materials and Methods and sequenced. (D) Northern blots of mRNA prepared from adult fish. Fish were probed either with full-length cDNA (lane 1) or a 207-bp fragment from the 3′UTR of zfAPEX1a (lane 2). The full-length cDNA probe identified both mRNA species (2,100 and 1,400 bp in length), whereas the probe from the 3′UTR identified only the larger mRNA species.