[1] European Bioinformat Inst EMBL EBI, European Mol Biol Lab, Wellcome Genome Campus, Hinxton CB10 1SD, Cambs, England
[2] Wellcome Sanger Inst, Wellcome Genome Campus, Hinxton CB10 1RQ, Cambs, England
[3] Swiss Fed Inst Technol, Inst Mol Syst Biol, Dept Biol, CH-8093 Zurich, Switzerland
[4] Columbia Univ, Dept Syst Biol, New York, NY 10027 USA