Yeast two-hybrid analysis has been applied for detecting the interactions in the entire proteome of several model organisms. Stelzl et al. have now applied an automated yeast two-hybrid interaction mating assay to test more than 5500 human proteins (excluding those with transmembrane domains). The analysis yielded 3269 interactions, which were then scored using a confidence rating system based on six criteria, including presence of the orthologous interactions in model organism data sets, the occurrence of interactions in loops containing three or four proteins (believed to be a common property of biological interaction networks), and annotation of the interacting proteins with Gene Ontology (GO) terms for localization and cellular function. Of the 3269 interactions, 911 met three or more of the criteria and were classified as high confidence. The network was also compared with the regulatory pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG), and 66 proteins were mapped into pathways based on their position as bridges linking two or more proteins within a pathway. Two of these, ANP32A and CRMP1, were mapped into the Wnt pathway and were verified using a reporter gene assay in cells transfected to overexpress the Wnt regulator Dvl, which stimulates Wnt reporter gene expression. Both ANP32A and CRPM1 inhibited Dvl-stimulated reporter gene expression, which suggests that these proteins are novel inhibitory regulators of the Wnt pathway. Thus, in addition to allowing analysis of the network properties of a human proteome interaction network, this large-scale analysis of the human proteome also revealed novel regulators of cell signaling.
U. Stelzl, U. Worm, M. Lalowski, C. Haenig, F. H. Brembeck, H. Goehler, M. Stroedicke, M. Zenkner, A. Schoenherr, S. Koeppen, J. Timm, S. Mintzlaff, C. Abraham, N. Bock, S. Kietzmann, A. Goedde, E. Toksöz, A. Droege, S. Krobitsch, B. Korn, W. Birchmeier, H. Lehrach, E. E. Wanker, A human protein-protein interaction network: A resource for annotating the proteome. Cell 122, 957-968 (2005). [PubMed]