European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. charles.girardot@embl.de|European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. charles.girardot@embl.de|European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. charles.girardot@embl.de|European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. charles.girardot@embl.de|European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. charles.girardot@embl.de