The sequence and organization of Ddp2, a high-copy-number nuclear plasmid of Dictyostelium discoideum

Martin B. Slade, Andy C. M. Chang, Keith L. Williams*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


The complete nucleotide sequence of the plasmid Ddp2 found in the nucleus of the simple eukaryoteDictyostelium 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 2μ plasmid which also possesses inverted repeat sequences. Ddp2 has a structure similar to that of plasmid pDG1, found in an unidentified isolate ofDictyostelium, 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.

Original languageEnglish
Pages (from-to)195-207
Number of pages13
Issue number3
Publication statusPublished - Nov 1990


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