Rolling-circle transposons in eukaryotes.
All eukaryotic DNA transposons reported so far belong to a single category of elements transposed by the so-called "cut-and-paste" mechanism. Here, we report a previously unknown category of eukaryotic DNA transposons, Helitron, which transpose by rolling-circle replication. Autonomous Helitrons encode a 5'-to-3' DNA helicase and nuclease/ligase similar to those encoded by known rolling-circle replicons. Helitron-like transposons have conservative 5'-TC and CTRR-3' termini and do not have terminal inverted repeats. They contain 16- to 20-bp hairpins separated by 10--12 nucleotides from the 3'-end and transpose precisely between the 5'-A and T-3', with no modifications of the AT target sites. Together with their multiple diverged nonautonomous descendants, Helitrons constitute approximately 2% of both the Arabidopsis thaliana and Caenorhabditis elegans genomes and also colonize the Oriza sativa genome. Sequence conservation suggests that Helitrons continue to be transposed.
Kapitonov
V V
VV
Genetic Information Research Institute, 2081 Landings Drive, Mountain View, CA 94043, USA. vladimir@charon.girinst.org
Jurka
J
J
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics; D004265:DNA Helicases / Q000235:genetics*; D004261:DNA Replication; D004251:DNA Transposable Elements; D018509:DNA, Helminth; D018744:DNA, Plant; D004268:DNA-Binding Proteins / Q000235:genetics; D005057:Eukaryotic Cells; D019143:Evolution, Molecular; D018745:Genome, Plant; D008969:Molecular Sequence Data; D051716:Replication Protein A
D004251:DNA Transposable Elements; D018509:DNA, Helminth; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D051716:Replication Protein A; D004265:DNA Helicases