Site-specific recombination determined by I-SceI, a mitochondrial group I intron-encoded endonuclease expressed in the yeast nucleus

Genetics. 1992 Mar;130(3):451-60. doi: 10.1093/genetics/130.3.451.


The Saccharomyces cerevisiae mitochondrial endonuclease I-SceI creates a double-strand break as the initiating step in the gene conversional transfer of the omega+ intron to omega- DNA. We have expressed a galactose-inducible synthetic I-SceI gene in the nucleus of yeast that also carries the I-SceI recognition site on a plasmid substrate. We find that the galactose-induced I-SceI protein can be active in the nucleus and efficiently catalyze recombination. With a target plasmid containing direct repeats of the Escherichia coli lacZ gene, one copy of which is interrupted by a 24-bp cutting site, galactose induction produces both deletions and gene conversions. Both the kinetics and the proportion of deletions and gene conversions are very similar to analogous events initiated by a galactose-inducible HO endonuclease gene. We also find that, in a rad52 mutant strain, the repair of double-strand breaks initiated by I-SceI and by HO are similarly affected: the formation of deletions is reduced, but not eliminated. Altogether, these results suggest either that the two endonucleases act in the same way after double-strand break formation or that the two endonucleases are not involved in subsequent steps.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • Blotting, Southern
  • Cell Nucleus / enzymology*
  • Chromosome Deletion
  • Cloning, Molecular
  • DNA Damage
  • DNA Repair
  • DNA, Fungal / metabolism
  • Deoxyribonucleases, Type II Site-Specific / genetics
  • Deoxyribonucleases, Type II Site-Specific / metabolism*
  • Escherichia coli / genetics
  • Gene Conversion
  • Gene Expression
  • Introns
  • Mitochondria / enzymology*
  • Molecular Sequence Data
  • Mutation
  • Plasmids
  • Recombination, Genetic*
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae Proteins


  • DNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • HO protein, S cerevisiae
  • SCEI protein, S cerevisiae
  • Deoxyribonucleases, Type II Site-Specific