Going from gene sequence to protein function presents a great challenge to genome biology. In the September 15 EMBO Reports, Simpson et al. suggest that the systematic identification of subcellular localization can significantly enhance our ability to assign functions to unknown ORFs (EMBO Reports 2000, 1:287-292). Simpson et al. outline a strategy for such an approach. They adapted the Gateway cloning system to allow rapid, directional cloning of ORFs by recombination, and generate amino- and carboxy- terminal GFP (green fluorescence protein) fusions. The authors used protein localization in living cells to follow the GFP-tagged proteins and to categorize clones for further study. More than 80% of proteins localized to recognized structures such as the cytosol (18%), nucleus (12%), secretory pathway (28%), mitochondria (5%) or the cytoskeleton (3%). Combining compartmentalization data with bioinformatic analysis of the cDNA sequences offers a promising strategy for predicting protein function. The...