title: A site-specific DNA endonuclease specified by one of two ORFs encoded by a group I intron in Dictyostelium discoideum mitochondrial DNA.
abstract: The second intron (DdOX1/2.2) of Dictyostelium discoideum cytochrome oxidase subunit 1/2 fused gene has two free-standing ORF genes (Dd ai2a and Dd ai2b) in a loop, which have similar amino acid sequences and are homologous to aI4 DNA endonuclease (I-SceII) of Saccharomyces cerevisiae. To elucidate the functions of these ORFs, we cloned the ORFs into an expression vector and introduced the composite vectors into E. coli. The expression of Dd ai2a in E. coli caused growth inhibition and degradation of the E. coli genomic DNA. To determine whether Dd ai2a protein is a homing type DNA endonuclease, the ability to cleave the homing site of its intron in vivo was examined. Dd ai2a cleaved only one strand of intronless DNA sequence at the site which coincides with the I-SceII cleavage recognition site. We suppose that Dd ai2a functions actually as a homing type DNA endonuclease in D. discoideum mitochondria by virtue of other factors. To obtain further information about the relationship between the existence of introns and the mating system, we carried out in vitro self-splicing assay and polymerase chain reaction analysis using 13 strains of the cellular slime mold.
authors.affiliation: Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ogawa
authors.forename: K
authors.initials: K
authors.lastname: Naito
authors.forename: K
authors.initials: K
authors.lastname: Angata
authors.forename: T
authors.initials: T
authors.lastname: Morio
authors.forename: H
authors.initials: H
authors.lastname: Urushihara
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000378:metabolism; D004272:DNA, Mitochondrial; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development; D007438:Introns; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins; D012326:RNA Splicing
chemical_list: D004269:DNA, Bacterial; D004272:DNA, Mitochondrial; D015800:Protozoan Proteins; C107041:Ai2a endonuclease, Dictyostelium; D004706:Endodeoxyribonucleases