Protein Expression Library Resources for Proteome Studies

There are several public projects worldwide with the goal of creating representative full-length cDNA clone collections, notably the NIH Mammalian Gene Collection (MGC) project and the Mouse Gene Encyclopedia Project sponsored by the RIKEN Institute in Japan. These projects have taken the approach of sifting through large numbers of cDNA clones, e.g. from tissue-specific libraries, to identify unique full-length cDNA clones. There are, additionally, independent efforts to create ORF clone collections for use as expression tools. These include the FLEXGene effort led by the Institute of Proteomics at Harvard Medical School (HIP), the Caenorhabditis elegans ORFeome Project, and the Ressourcenzentrum fûr Genomforschung (RZPD) ORF clone collection. These clone collections are available at this time as either cDNA clones or ORF clones. While cDNA clones are the most straightforward to create, they have important limitations as experimental tools. The cloned sequences serve not only as a tool to assist in the assignment of gene boundaries and the identification of splice isoforms, but also serve as the starting point for a new kind of genome-scale tool: an arrayed, sequence-validated, and full-length ORF clone collection that is highly representative of the gene content of an organism. These types of collections are under development for human, mouse, several of the important model organisms, and an important human pathogen, P. aeruginosa.