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International Summer School
From Genome to Life:
Structural, Functional and Evolutionary approaches
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OGATA
Hiroyuki |
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Laboratory of Structural & Genetic Information, CNRS UMR1889, 31 Chemin Joseph Aiguier, Marseille, 13402 Cedex 20, France title: Comparative genome analysis: example of Rickettsia Our recent comparative analysis of Rickettsia conorii (1.3 Mbp) and R. prowazekii (1.1 Mbp) has revealed unexpected mechanisms of genome evolution [1]. Both Rickettsia exhibited palindromic repeats (100-150 bases) dispersed in their genome. Surprisingly, many of those palindromic sequences were identified within predicted ORFs. A systematic analysis reveals three different palindromic sequence families (RPE-1, 2 and 3) exhibiting this phenomenon. We verified that those repeats are indeed translated and retained as supplementary amino-acid sequences in the final proteins, without affecting their fold and function [2]. Thus RPEs appear to represent a new class of selfish DNA encoding a "selfish peptide". The comparison of the two genomes also evidenced a very gradual nature of the genome reduction process. We identified different intermediates from intact ORFs: a truncated protein, transcribed split ORFs, transcriptionally inactive split ORFs, decayed but still recognizable ORFs, and complete gene elimination. The evolutionary significance of those phenomena will be discussed. [1] Ogata et al.: Science, 290, 347-350, 2000; Science, 291, 252-253, 2001; Science, 293, 2093-2098, 2001; 2002 (submitted). [2]
Monchois et al.: 2002 (submitted). |
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ADDITIONAL DATA |
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HTTP LINK:
The Rickettsia genome database (RicBase) relevant to my talk is available through: |