To facilitate studies of the yeast proteome, we cloned 5800 open reading frames and overexpressed and purified their corresponding proteins. The proteins were printed onto slides at high spatial density to form a yeast proteome microarray and screened for their ability to interact with proteins and phospholipids. We identified many new calmodulin- and phospholipid-interacting proteins; a common potential binding motif was identified for many of the calmodulin-binding proteins. Thus, microarrays of an entire eukaryotic proteome can be prepared and screened for diverse biochemical activities. The microarrays can also be used to screen protein-drug interactions and to detect posttranslational modifications.

Protein localization data are a valuable information resource helpful in elucidating eukaryotic protein function. Here, we report the first proteome-scale analysis of protein localization within any eukaryote. Using directed topoisomerase I-mediated cloning strategies and genome-wide transposon mutagenesis, we have epitope-tagged 60% of the Saccharomyces cerevisiae proteome. By high-throughput immunolocalization of tagged gene products, we have determined the subcellular localization of 2744 yeast proteins. Extrapolating these data through a computational algorithm employing Bayesian formalism, we define the yeast localizome (the subcellular distribution of all 6100 yeast proteins). We estimate the yeast proteome to encompass ∼5100 soluble proteins and >1000 transmembrane proteins. Our results indicate that 47% of yeast proteins are cytoplasmic, 13% mitochondrial, 13% exocytic (including proteins of the endoplasmic reticulum and secretory vesicles), and 27% nuclear/nucleolar. A subset of nuclear proteins was further analyzed by immunolocalization using surface-spread preparations of meiotic chromosomes. Of these proteins, 38% were found associated with chromosomal DNA. As determined from phenotypic analyses of nuclear proteins, 34% are essential for spore viability-a percentage nearly twice as great as that observed for the proteome as a whole. In total, this study presents experimentally derived localization data for 955 proteins of previously unknown function: nearly half of all functionally uncharacterized proteins in yeast. To facilitate access to these data, we provide a searchable database featuring 2900 fluorescent micrographs at http://ygac.med.yale.edu. A global understanding of the molecular mechanisms underpinning cell biology necessitates an understanding not only of an organism's genome but also of the protein complement encoded within this genome (the proteome). In the past, data regarding an organism's proteome have typically been accumulated piecemeal through studies of a single protein or cell pathway. Genomic methodologies have altered this paradigm: a variety of approaches are now in place by which proteins may be directly analyzed on a proteome-wide scale. Chromatography-coupled mass spectrometry (Gygi et al. 1999;Washburn et al. 2001), large-scale two-hybrid screens (Uetz et al. 2000;Ito et al. 2001;Tong et al. 2002), immunoprecipitation/mass spectrometric analysis of protein complexes (Gavin et al. 2002;Ho et al. 2002), and protein microarray technologies (MacBeath and Schreiber 2000;Zhu et al. 2000Zhu et al. , 2001 are yielding unprecedented quantities of protein data. Recent genomic techniques combining microarray technologies with either chromatin immunoprecipitation (Ren et al. 2000;Iyer et al. 2001) or targeted DNA methylation (van Steensel et al. 2001) have been used to globally map binding sites of chromosomal proteins in vivo. Initiatives are even underway to automate and industrialize processes by which protein structures may be solved, potentially providing a library of structural...

We have mapped the chromosomal binding site distribution of a transcription factor in human cells. The NF-B family of transcription factors plays an essential role in regulating the induction of genes involved in several physiological processes, including apoptosis, immunity, and inflammation. The binding sites of the NF-B family member p65 were determined by using chromatin immunoprecipitation and a genomic microarray of human chromosome 22 DNA. Sites of binding were observed along the entire chromosome in both coding and noncoding regions, with an enrichment at the 5 end of genes. Strikingly, a significant proportion of binding was seen in intronic regions, demonstrating that transcription factor binding is not restricted to promoter regions. NF-B binding was also found at genes whose expression was regulated by tumor necrosis factor ␣, a known inducer of NF-B-dependent gene expression, as well as adjacent to genes whose expression is not affected by tumor necrosis factor ␣. Many of these latter genes are either known to be activated by NF-B under other conditions or are consistent with NF-B's role in the immune and apoptotic responses. Our results suggest that binding is not restricted to promoter regions and that NF-B binding occurs at a significant number of genes whose expression is not altered, thereby suggesting that binding alone is not sufficient for gene activation.U nderstanding the targets regulated by transcription factors and where they bind relative to these targets in an unbiased fashion in mammalian cells is highly desirable. We and others have developed a procedure for mapping in vivo targets of transcription factors by chromatin immunoprecipitation (ChIP) with antibodies to a transcription factor of interest to isolate protein-bound DNA, followed by probing a microarray containing genomic DNA sequences with the immunoprecipitated DNA (ChIP chip) (1-3). This approach was first used successfully in yeast and has more recently been used in a limited fashion to identify transcription factor binding sites in mammalian cells (4-6). However, a large-scale, unbiased global analysis of the distribution of mammalian transcription factor binding sites along large genomic regions has not been previously explored.In this study we employ a microarray containing the entire nonrepetitive sequence of chromosome 22 to determine the chromosome-wide binding profile for the transcription factor NF-B. The NF-B͞Rel family of transcription factors plays an essential role in regulating the induction of genes involved in several physiological processes, including immune and inflammatory responses (7,8), and the activation pathway has been studied extensively over the last two decades (9, 10). Numerous NF-B target genes have also been identified; however, it remains unclear how many of these are direct targets of the transcription factor (11).There are five mammalian NF-B family members (p50, p52, RelA͞p65, RelB, and c-rel), all of which function as homo-or heterodimers. The different dimers exhibit varying binding aff...

Economical methods by which gene function may be analysed on a genomic scale are relatively scarce. To fill this need, we have developed a transposon-tagging strategy for the genome-wide analysis of disruption phenotypes, gene expression and protein localization, and have applied this method to the large-scale analysis of gene function in the budding yeast Saccharomyces cerevisiae. Here we present the largest collection of defined yeast mutants ever generated within a single genetic background--a collection of over 11,000 strains, each carrying a transposon inserted within a region of the genome expressed during vegetative growth and/or sporulation. These insertions affect nearly 2,000 annotated genes, representing about one-third of the 6,200 predicted genes in the yeast genome. We have used this collection to determine disruption phenotypes for nearly 8,000 strains using 20 different growth conditions; the resulting data sets were clustered to identify groups of functionally related genes. We have also identified over 300 previously non-annotated open reading frames and analysed by indirect immunofluorescence over 1,300 transposon-tagged proteins. In total, our study encompasses over 260,000 data points, constituting the largest functional analysis of the yeast genome ever undertaken.

A DNA microarray representing nearly all of the unique sequences of human Chromosome 22 was constructed and used to measure global-transcriptional activity in placental poly(A) + RNA. We found that many of the known, related and predicted genes are expressed. More importantly, our study reveals twice as many transcribed bases as have been reported previously. Many of the newly discovered expressed fragments were verified by RNA blot analysis and a novel technique called differential hybridization mapping (DHM). Interestingly, a significant fraction of these novel fragments are expressed antisense to previously annotated introns. The coding potential of these novel expressed regions is supported by their sequence conservation in the mouse genome. This study has greatly increased our understanding of the biological information encoded on a human chromosome. To facilitate the dissemination of these results to the scientific community, we have developed a comprehensive Web resource to present the findings of this study and other features of human Chromosome 22 at http://array.mbb.yale.edu/chr22.