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Formation and repair of O 6 ‐methylguanine in recombination hot spots of plant chromosomes
Author(s) -
Baranczewski Pawel,
Nehls Peter,
Rieger Rigomar,
Pich Uta,
Rajewsky Manfred F.,
Schubert Ingo
Publication year - 1997
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/(sici)1098-2280(1997)29:4<394::aid-em8>3.0.co;2-a
Subject(s) - mutagen , chromatid , biology , microbiology and biotechnology , genetics , vicia faba , metaphase , dna , euchromatin , prophase , dna repair , heterochromatin , meiosis , chromosome , botany , chromatin , gene
Mutagen‐induced chromatid aberrations are not randomly distributed along the metaphase chromosomes. In the field bean ( Vicia faba ), defined late‐replicating and transcriptionally inactive heterochromatic regions are preferentially involved. After exposure to the alkylating agent N ‐methyl‐ N ‐nitrosourea (MNU) (10 −3 M, 1 hour), 70% of all aberrations are clustered within 6 segments containing tandemly repeated Fok I elements of 59 bp, which comprise ∼ 10% of the genome. Using immuno‐slot‐blot analyses, we have studied the frequency of O 6 ‐methylguanine ( O 6 ‐MeG), a mutagenic lesion important for aberration induction, in total genomic DNA as well as in Fok I sequences of the field bean after exposure to MNU. In either case, similar numbers of adducts per nucleotide were found immediately after treatment as well as after 18 hours of recovery, when most adducts were removed and significant amounts of chromatid aberrations were detectable. Peculiarities of long Fok I element arrays (e.g., formation of specific tertiary structures), resulting in error‐prone recombination repair, rather than preferential formation or delayed repair of O 6 ‐MeG are apparently responsible for aberration clustering in these hot spot regions. Environ. Mol. Mutagen. 29:394–399, 1997 © 1997 Wiley‐Liss, Inc.