title: Analysis of the functions of recombination-related genes in the generation of large chromosomal deletions by loop-out recombination in Aspergillus oryzae.
abstract: Loop-out-type recombination is a type of intrachromosomal recombination followed by the excision of a chromosomal region. The detailed mechanism underlying this recombination and the genes involved in loop-out recombination remain unknown. In the present study, we investigated the functions of ku70, ligD, rad52, rad54, and rdh54 in the construction of large chromosomal deletions via loop-out recombination and the effect of the position of the targeted chromosomal region on the efficiency of loop-out recombination in Aspergillus oryzae. The efficiency of generation of large chromosomal deletions in the near-telomeric region of chromosome 3, including the aflatoxin gene cluster, was compared with that in the near-centromeric region of chromosome 8, including the tannase gene. In the Δku70 and Δku70-rdh54 strains, only precise loop-out recombination occurred in the near-telomeric region. In contrast, in the ΔligD, Δku70-rad52, and Δku70-rad54 strains, unintended chromosomal deletions by illegitimate loop-out recombination occurred in the near-telomeric region. In addition, large chromosomal deletions via loop-out recombination were efficiently achieved in the near-telomeric region, but barely achieved in the near-centromeric region, in the Δku70 strain. Induction of DNA double-strand breaks by I-SceI endonuclease facilitated large chromosomal deletions in the near-centromeric region. These results indicate that ligD, rad52, and rad54 play a role in the generation of large chromosomal deletions via precise loop-out-type recombination in the near-telomeric region and that loop-out recombination between distant sites is restricted in the near-centromeric region by chromosomal structure.
authors.affiliation: Noda Institute for Scientific Research, Noda City, Chiba, Japan. ttakahashi@mail.kikkoman.co.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ogawa
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Koyama
mesh_terms: D001236:Aspergillus oryzae / Q000235:genetics* / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000235:genetics; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D002872:Chromosome Deletion; D015825:Chromosomes, Fungal / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D053903:DNA Breaks, Double-Stranded; D004271:DNA, Fungal / Q000235:genetics; D004720:Endonucleases / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D055786:Gene Knockout Techniques; D011995:Recombination, Genetic; D016615:Telomere / Q000235:genetics / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D004720:Endonucleases; D002265:Carboxylic Ester Hydrolases; C022711:tannase