  Understanding functional associations among genes discovered in sequencing
projects is a key issue in post-genomic biology. However, reliable
interpretation of the protein interaction data has been difficult. In this
work, we show that if two proteins share significantly larger number of common
interaction partners than random, they have close functional associations.
Analysis of publicly available data from Saccharomyces cerevisiae reveals more
than 2800 reliable functional associations, 29% of which involve at least one
unannotated protein. By further analyzing these associations, we derive
tentative functions for 81 unannotated proteins with high certainty.
