Proteins identified from each subcellular fraction were classified based on their Gene Ontology annotations using GeneTrail [55] . Additionally, k-means clustering analysis was performed for the differentially regulated proteins in each subcellular fraction using Chipster, an open source data analysis tool (http://chipster. sourceforge.net). Clustering was done based on the relative quantitation results from the iTRAQ experiments, and a suitable number of clusters for each subcellular fraction was determined by studying the cluster profiles. Protein-protein interaction networks for a selected group of proteins was created using String [56] .