Selfish DNA Parasitizing Protein-Coding Genes of Rickettsia
Hiroyuki OGATA, Stéphane AUDIC, Jean-Michel CLAVERIE
Information Génétique et Structurale,CNRS-AVENTIS UMR1889,
31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
Rickettsia conorii is an obligate intracellular bacterial pathogene,
transmitted by ticks and causing Mediterranean spotted fever in human.
The whole genome sequencing of R. conorii has been completed.
The analysis of this sequence allowed the discovery of a new repeated
element capable of parasitizing protein-coding regions at a high efficiency
(1,2). The repeat named Rickettsia palindromic element, RPE, is a 150
bp long self-complimentary sequence, capable of forming a hairpin-like
secondary structure. Of 45 full-length occurrences of the RPE in the
R. conorii genome, 24 are found in different ORFs that are likely to
encode functional proteins. In R. prowazekii, RPE occurs nine times in
coding and only once in non-coding regions. We also identified RPEs in ORFs
in R. felis and R. helvetica. Until now selfish DNA has been
considered to contribute genome evolution, solely by shuffling pre-existing
genes or by creating new regulatory sequences. The finding of RPE in different
protein coding sequences suggests that selfish DNA may contribute to the
de novo creation of new protein sequence and function.
1. Ogata et al., Science, 290, 347-350 (2000).
2. Ogata et al., Science, 291, 252-253 (2001).
Journées "Évolution Biologique"
(June 27-29, 2001, Marseille, France)