Research article

An open reading frame in intron seven of the sea urchin DNA-methyltransferase gene codes for a functional AP1 endonuclease

Anna Valentina CIOFFI, Diana FERRARA, Maria Vittoria CUBELLIS, Francesco ANIELLO, Marcella CORRADO, Francesca LIGUORI, Alessandro AMOROSO, Laura FUCCI, Margherita BRANNO


Analysis of the genome structure of the Paracentrotus lividus (sea urchin) DNA methyltransferase (DNA MTase) gene showed the presence of an open reading frame, named METEX, in intron 7 of the gene. METEX expression is developmentally regulated, showing no correlation with DNA MTase expression. In fact, DNA MTase transcripts are present at high concentrations in the early developmental stages, while METEX is expressed at late stages of development. Two METEX cDNA clones (Met1 and Met2) that are different in the 3′ end have been isolated in a cDNA library screening. The putative translated protein from Met2 cDNA clone showed similarity with Escherichia coli endonuclease III on the basis of sequence and predictive three-dimensional structure. The protein, overexpressed in E. coli and purified, had functional properties similar to the endonuclease specific for apurinic/apyrimidinic (AP) sites on the basis of the lyase activity. Therefore the open reading frame, present in intron 7 of the P. lividus DNA MTase gene, codes for a functional AP endonuclease designated SuAP1.

  • development
  • DNA repair
  • glycosylase
  • Paracentrotus lividus
  • splicing


  • 1 These authors contributed equally to this work.

  • Abbreviations used: ORF, open reading frame; LINE, long interspersed nuclear element; DNA MTase, DNA methyltransferase; AP, apurinic/apyrimidinic; SSC, sodium saline citrate; TBE, Tris-borate-EDTA; LB, Luria—Bertoni (broth); 3′UTR, 3′ untranslated region; SuAP1, sea urchin endonuclease III homologue 1; Exo, exonuclease; GST, glutathione S-transferase.