We wish to thank G.I. Chen, M. Mullin, M.J. Kean, T.M. Greco, T. Srikumar and Y.-C. Tsai for contributing published data and S. Saha and J.-E. Dazard for constructive comments. We thank A. Stefanovic, M. Planyavsky, A. Stukalov, A.J. Guise, A.C. Müller, A. Pichlmair, B. Larsen, C. Knoll, C.L. Baumann, E.L. Rudashevskaya, F. Grebien, F.P. Breitwieser, H.G. Budayeva, J.W. Bigenzahn, M. Bruckner, M. Licciardello, M.L. Huber, M. Tucholska, N. Venturini, O. Rocks, O. Stein, P. Joshi, R. Giambruno, R. Sacco, S. Zhang, T. Stasyk and V. Nguyen for help with sample analysis.

This work was supported by grants from the US National Institutes of Health (NIH 5R01GM94231 to A.-C.G. and A.I.N.; DP1DA026192 and HL112618-01 to I.M.C.), the Canadian Institutes of Health Research (CIHR MOP-84314 to A.-C.G.; MOP-82851 to B.C.), the government of Ontario via a Global Leadership Round in Genomics and Life Sciences (T.P. and A.-C.G.), the Austrian Academy of Sciences (K.L.B., J.C. and G.S.-F.), the Austrian Federal Ministry for Science and Research (Gen-Au projects, APP-III and BIN-III; K.L.B. and G.S.-F., no. 820965; J.C. and K.L.B., no. 820962), the European Research Council (G.S.-F.; ERC-2009-AdG-250179-i-FIVE), the Austrian Science Fund FWF (G.S.-F., J.C. and K.L.B.; P24321-B21 and P22282-B11), the European Molecular Biology Organization long-term fellowship (G.S.-F., J.C. and K.L.B.; ATLF463-2008), The Netherlands Proteomics Center (T.Y.L., V.A.H., S.M. and A.J.R.H.), the European Union 7th Framework Program (PRIME-XS project, grant no. 262067; T.Y.L., V.A.H., S.M., R.A. and A.J.R.H.), the Stowers Institute for Medical Research, and the Human Frontier Science Program (RGY0079/2009-C to I.M.C.). A.-C.G. is the Canada Research Chair in Functional Proteomics and the Lea Reichmann Chair in Cancer Proteomics; B.R. is the Canada Research Chair in Proteomics and Molecular Medicine. R.M.E. acknowledges salary support from the Cleveland Foundation and NIH 1R21 CA16006001A1. J.-P.L. and R.D.B. were supported by CIHR postdoctoral awards. N.A.S.-D. was supported by a TD Bank postdoctoral fellowship.