THE HUMAN GENOME ENCODES INSTRUCTIONS TO MAKE APPROXIMATELY 20,000 DIFFERENT PROTEINS – IN AGGREGATE, THE PROTEOME – WHOSE ACTIVITIES MEDIATE MOST BIOLOGICAL PROCESSES AT BOTH CELLULAR AND ORGANISMAL LEVELS. THE PROTEOME CAN BE VIEWED AS CONSTELLATIONS OF INTERACTING PROTEINS THAT ASSEMBLE TO FORM MYRIAD COMPLEXES, COMPARTMENTS, AND SIGNAL TRANSDUCTION PATHWAYS THAT ORGANIZE INDIVIDUAL PROTEINS ACCORDING TO SHARED BIOLOGICAL FUNCTION. THUS, UNDERSTANDING THE INTERACTOME – THE COMPLETE SET OF HUMAN PROTEIN-PROTEIN INTERACTIONS AND THE CONDITIONS IN WHICH THEY OCCUR – WILL BE ESSENTIAL TO DEVELOPING A SYSTEMS-LEVEL UNDERSTANDING OF THE HUMAN CELL.