Visualization of biochemical networks in living cells

Functional annotation of novel genes can be achieved by detection of intera ctions of their encoded proteins with known proteins followed by assays to validate that the gene participates in a specific cellular function. We rep ort an experimental strategy that allows for detection of protein interacti ons and functional assays with a single reporter system. Interactions among biochemical network component proteins are detected and probed with stimul ators and inhibitors of the network. In addition, the cellular location of the interacting proteins is determined. We used this strategy to map a sign al transduction network that controls initiation of translation in eukaryot es, We analyzed 35 different pairs of full-length proteins and identified 1 4 interactions, of which five have not been observed previously, suggesting that the organization of the pathway is more ramified and integrated than previously shown. Our results demonstrate the feasibility of using this str ategy in efforts of genomewide functional annotation.