Nature 415, 871–880 (2002).

In this Article, the author Andreas Düsterhöft was mistakenly omitted: his name and affiliation (footnote 6) should have been inserted between M. Fuchs and C. Fritzc in the author list. In addition, the name of L. Cerutti (in the last line of the author list) was misspelled. On p874 in the penultimate sentence of the ‘Intergene regions’ section, “tandemly oriented genes” should read “divergently oriented genes.”