title: Identification of a type I Ca2+/Mg2+-dependent endonuclease induced in maize cells exposed to camptothecin.
abstract: BACKGROUND
  Camptothecin is a plant alkaloid that specifically binds topoisomerase I, inhibiting its activity and inducing double stranded breaks in DNA and activating the cell responses to DNA damage.
  
  
  RESULTS
  Maize cultured cells were incubated in the presence of different concentrations of camptothecin. Camptothecin inhibits cultured cell growth, induces genomic DNA degradation, and induces a 32 kDa Ca2+/Mg2+-dependent nuclease activity. This nuclease, we called CaMNUC32, is inhibited by Zn2+ and by acid pH, it is mainly localized in the nucleus and it cleaves single- and double-stranded DNA, with a higher activity against single-stranded DNA. Two-dimensional electrophoresis combined with mass spectrometry suggests that CaMNUC32 is a member of the type I S1/P1 nuclease family. This type of nucleases are usually Zn2+-dependent but our results support previous indications that S1-type nucleases have a wide variety of enzyme activities, including Ca2+/Mg2+-dependent.
  
  
  CONCLUSIONS
  We have identified and characterized CaMNUC32, a 32 kDa Ca2+/Mg2+-dependent nuclease of the S1/P1 family induced by the topoisomerase I inhibitor camptothecin in maize cultured cells.
authors.affiliation: Department of Molecular Genetics, Centre for Research in Agricultural Genomics CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Spain. carlos.vicient@cragenomica.es.
authors.forename: Núria
authors.initials: N
authors.lastname: Sánchez-Pons
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Vicient
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D002166:Camptothecin / Q000494:pharmacology; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D003850:Deoxyribonuclease I / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D007527:Isoenzymes / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology*; D010802:Phylogeny; D059828:Plant Cells / Q000187:drug effects / Q000201:enzymology*; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D003313:Zea mays / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development
chemical_list: D007527:Isoenzymes; D003850:Deoxyribonuclease I; D008274:Magnesium; D002118:Calcium; D002166:Camptothecin