《计算系统生物学导论》系统生物学导论-2012-4.pptVIP

Determining the tissue speci?city of human protein interactions We then used gene expression data (Su et al, 2004) to determine the cells and tissues of the human body in whicheach of these interactions can occur (Figure 1A). If two genes are co-expressed in a cell, then under some condition their products can physically interact in that cell. However, if two proteins are not expressed in a tissue, then the interaction cannot occur in this tissue. Tissue speci?c and recently evolved proteins make few protein interactions We ?nd that more tissue-speci?c proteins make fewer interactions than widely expressed proteins (Figure 1B). We ?nd that more-recently evolved proteins have fewer interactions than ancient proteins, but that the relation-ship between tissue speci?city and interaction degree is seen for both sets of proteins (Figure 1C). That is, the older a protein is, and the more tissues in which it is expressed, the more protein interactions it is likely to have. The most tissue-speci?c proteins normally interact with core cellular components We next analyzed the extent to which tissue-speci?c proteins interact with the most widely expressed proteins. We ?nd that even when only considering the most tissue-restricted proteins (proteins expressed in p10/79 tissues), most of them are known to interact directly with universally expressed human proteins (Figure 2A). Thus, most tissue-speci?c proteins can function by directly contacting components of the core cellular machinery Most universally expressed proteins have tissue-speci?c protein interactions Constitutively expressed proteins are often considered as important for ‘housekeeping’ biological processes that are required in all cells. However, nearly all of the most widely expressed proteins have interactions with other proteins that are not themselves universally expressed (Figure 2B). That is, most universally expressed proteins have physical interactions that can only occur in a re