title: The sequence and organization of Ddp2, a high-copy-number nuclear plasmid of Dictyostelium discoideum.
abstract: The complete nucleotide sequence of the plasmid Ddp2 found in the nucleus of the simple eukaryote Dictyostelium discoideum is reported. This 5852-bp plasmid contains a 2661-bp open reading frame (ORF), named the "Rep gene," and 501-bp imperfect inverted repeats. A 1762-bp section of Ddp2, which includes one of the 501-bp repeat sequences, could be deleted without abolishing extrachromosomal replication. Deletion of the second 501-bp repeat, or interruption of the Rep gene, removed the ability to replicate extrachromosomally. We suggest that Ddp2 encodes a protein, "REP," that positively regulates replication initiation, a regulatory mechanism different from that of the yeast 2 mu plasmid which also possesses inverted repeat sequences. Ddp2 has a structure similar to that of plasmid pDG1, found in an unidentified isolate of Dictyostelium, with a similar sized ORF and inverted repeats. A common evolutionary origin is suggested by considerable sequence homology between the ORFs of pDG1 and Ddp2.
authors.affiliation: School of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia.
authors.forename: M B
authors.initials: MB
authors.lastname: Slade
authors.forename: A C
authors.initials: AC
authors.lastname: Chang
authors.forename: K L
authors.initials: KL
authors.lastname: Williams
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000502:physiology*; D003001:Cloning, Molecular; D004261:DNA Replication; D004023:Dictyostelium / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014170:Transformation, Genetic