title: Tdd-4, a DNA transposon of Dictyostelium that encodes proteins similar to LTR retroelement integrases.
abstract: Tdd-4 is the first DNA transposon to be isolated from Dictyostelium discoideum. This element was isolated by insertion into a target plasmid. Two classes of elements were identified which include a 3.8 kb version and a 3.4 kb deleted version. Sequence analysis reveals that the 145 bp inverted terminal repeats contain the 5'-TGellipsisCA-3' conserved terminal dinucleotides found in prokaryotic transposons and integrated LTR retroelement DNA sequences. Tdd-4 open reading frames are assembled by removal of six introns. Introns 1-5 conform to the GT-AG rule, whereas intron 6 appears to be an AT-AA intron. Also, intron 6 undergoes an alternative 5' splicing reaction. The alternatively spliced region encodes 15 tandem SPXX repeats that are proposed to function as a DNA binding motif. By analogy to other transposons that encode two proteins from the same gene, the full-length Tdd-4 protein is the putative transposase and the truncated Tdd-4 protein is the putative transposition inhibitor. Protein database searches demonstrate Tdd-4 encoded proteins are unique for a DNA element by containing similarities to retroviral/retrotransposon integrases. The putative Tdd-4 transposase contains the same structural relationship as integrases by possessing an N-terminal HHCC motif, a central DDE motif and a C-terminal DNA-binding domain composed of the SPXX motif.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004251:DNA Transposable Elements; D016054:DNA, Protozoan; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics*; D019426:Integrases / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D015800:Protozoan Proteins / Q000235:genetics*; D018626:Retroelements; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D020079:Terminal Repeat Sequences