cDNA Cloning and Analysis of the Chicken Homolog (chApex1) of APEX Nuclease, a Multifunctional DNA Repair Enzyme

Abstract

We have cloned and analyzed the cDNA (chApex1) for the chicken homolog of APEX nuclease, a multifunctional DNA repair enzyme. Chicken Apex cDNA fragments were first amplified from Chick Embryo Lambda cDNA Library by nested PCR (polymerase chain reaction) using primers constructed on the basis of information of highly conserved regions of the amino acid sequences among mouse, rat and human APEX nuclease. Almost full-size chicken Apex cDNA was cloned from the Chick Embryo Lambda cDNA Library using the amplified chicken Apex cDNA fragments as a probe. The cloned cDNA was 1751 nucleotide long encoding a protein consisting of 300 amino acids with a predicted molecular mass of 33 kDa. The amino acid sequence exhibits a high homology with the sequence of the mammalian APEX nuclease (64%, 62% and 63% identities/300 amino acids with those of the human, mouse and rat APEX nuclease, respectively). The homologies of the amino acid sequences between chicken and mammalian APEX nucleases occurred along nearly the entire length of the sequences.