title: Genomic instability and mobile genetic elements in regions surrounding two discoidin I genes of Dictyostelium discoideum.
abstract: We have found that the genomic regions surrounding the linked discoidin I genes of various Dictyostelium discoideum strains have undergone rapid changes. Wild-type strain NC-4 has three complete discoidin I genes; its axenic derivative strain Ax-3L has duplicated a region starting approximately 1 kilobase upstream from the two linked genes and extending for at least 8 kilobases past the genes. A separately maintained stock, strain Ax-3K, does not have this duplication but has undergone a different rearrangement approximately 3 kilobases farther upstream. We show that there are repeat elements in these rapidly changing regions. At least two of these elements, Tdd-2 and Tdd-3, have characteristics associated with mobile genetic elements. The Tdd-3 element is found in different locations in related strains and causes a 9- to 10-base-pair duplication of the target site DNA. The Tdd-2 and Tdd-3 elements do not cross-hybridize, but they share a 22-base-pair homology near one end. At two separate sites, the Tdd-3 element has transposed into the Tdd-2 element, directly adjacent to the 22-base-pair homology. The Tdd-3 element may use this 22-base-pair region as a preferential site of insertion.
mesh_terms: D004251:DNA Transposable Elements; D004023:Dictyostelium / Q000235:genetics*; D000070821:Discoidins; D005656:Fungal Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D005796:Genes; D005809:Genes, Regulator; D008040:Genetic Linkage; D037102:Lectins; D015800:Protozoan Proteins; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D004251:DNA Transposable Elements; D000070821:Discoidins; D005656:Fungal Proteins; D037102:Lectins; D015800:Protozoan Proteins