R-loop-dependent rolling-circle replication and a new model for DNA concatemer resolution by mitochondrial plasmid mp1.
The mitochondrial (mt) plasmid mp1 of Chenopodium album replicates by a rolling-circle (RC) mechanism initiated at two double-stranded replication origins (dso1 and dso2). Two-dimensional gel electrophoresis and electron microscopy of early mp1 replication intermediates revealed novel spots. Ribonucleotide (R)-loops were identified at dso1, which function as a precursor for the RCs in vivo and in vitro. Bacteriophage T4-like networks of highly branched mp1 concatemers with up to 20 monomer units were mapped and shown to be mainly formed by replicating, invading, recombining and resolving molecules. A new model is proposed in which concatemers were separated into single units by a "snap-back" mechanism and homologous recombination. dso1 is a recombination hotspot, with sequence homology to bacterial Xer recombination cores. mp1 is a unique eukaryotic plasmid that expresses features of phages like T4 and could serve as a model system for replication and maintenance of DNA concatemers.
Backert
Steffen
S
Department of Botany and Microbiology, Auburn University, Auburn, AL 36849, USA. backert@mpiib-berlin.mpg.de
D001483:Base Sequence; D027463:Chenopodium album / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D015180:Electrophoresis, Gel, Two-Dimensional; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure*; D011995:Recombination, Genetic; D016415:Sequence Alignment
D004272:DNA, Mitochondrial