Resumen de IS 200: an old and still bacterial transposon
Carmen del Rosario Beuzón López, Daniela Chessa, Josep Casadesús Pursals
IS 200 is a mobile element found in a variety of eubacterial genera, such as Salmonella, Escherichia, Shigella, Vibrio, Enterococcus, Clostridium, Helicobacter, and Actinobacillus. In addition, IS200-like elements are found in archaea. IS 200 elements are very small (707–711 bp) and contain a single gene. Cladograms constructed with IS200 DNA sequences suggest that IS 200 has not spread among eubacteria by horizontal transfer; thus it may be an ancestral component of the bacterial genome. Self-restraint may have favored this evolutionary endurance; in fact, unlike typical mobile elements, IS 200 transposes rarely. Tight repression of transposase synthesis is achieved by a combination of mechanisms: inefficient transcription, protection from impinging transcription by a transcriptional terminator, and repression of translation by a stem-loop mRNA structure. A consequence of IS 200 self-restraint is that the number and distribution of IS 200
