PMID:9214648
| Citation |
Bierne, H, Ehrlich, SD and Michel, B (1997) Deletions at stalled replication forks occur by two different pathways. EMBO J. 16:3332-40 |
|---|---|
| Abstract |
Replication blockage induces non-homologous deletions in Escherichia coli. The mechanism of the formation of these deletions was investigated. A pBR322-mini-oriC hybrid plasmid carrying two E. coli replication terminators (Ter sites) in opposite orientations was used. Deletions which remove at least the pBR322 blocking site (named Ter1) occurred at a frequency of 2 x 10(-6) per generation. They fall into two equally large classes: deletions that join sequences with no homology, and others that join sequences of 3-10 bp of homology. Some 95% of the deletions in the former class resulted from the fusion of sequences immediately preceding the two Ter sites, indicating a direct role for blocked replication forks in their formation. These deletions were not found in a topA10 mutant, suggesting a topoisomerase I-mediated process. In contrast, deletions joining short homologous sequences were not affected by the topA10 mutation. However, the incidence of this second class of deletions increased 10-fold in a recD mutant, devoid of exonuclease V activity. This indicates that linear molecules are intermediates in their formation. In addition, approximately 50% of these deletions were clustered in the region flanking the Ter1 site. We propose that they are produced by repair of molecules broken at the blocked replication forks. |
| Links |
PubMed PMC1169949 Online version:10.1093/emboj/16.11.3332 |
| Keywords |
Base Sequence; DNA Replication; DNA Topoisomerases, Type I/genetics; DNA Topoisomerases, Type I/metabolism; Escherichia coli/genetics; Escherichia coli Proteins; Exodeoxyribonuclease V; Exodeoxyribonucleases/genetics; Models, Genetic; Molecular Sequence Data; Mutation; Nucleic Acid Conformation; Plasmids/genetics; Recombination, Genetic; Sequence Analysis, DNA; Sequence Deletion |
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