Abstract: The cell-based assays described in the present invention can be used to directly assess the sensitivity and specificity of the gene annotation reagent against its target, mapping genes and to determine if a non-targeted gene participates in a pathway of interest or is functionally linked to another gene or protein. Preferred assay embodiments include fluorescence or luminescence assays in intact (live or fixed) cells. Such fluorescence or luminescence assays include high-throughput or high-content assays for protein activity, subcellular localization, post-translational modifications, or interactions of proteins. Suitable assays may include protein-protein interaction assays; protein translocation assays; and post-translational modification assays. The invention can be used to assess the efficacy of any gene silencing experiment, and to map novel genes into biochemical pathways, and to identify novel pharmaceutical targets.

Abstract: The present invention provides protein fragment complementation assays for drug discovery, in particular to identify compounds that activate or inhibit cellular pathways. Based on the selection of an interacting protein pair combined with an appropriate PCA reporter, the assays may be run in high-throughput or high-content mode and may be used in automated screening of libraries of compounds. The interacting pair may be selected by cDNA library screening; by gene-by-gene interaction mapping; or by prior knowledge of a pathway. Fluorescent and luminescent assays can be constructed using the methods provided herein. The selection of suitable PCA reporters for high-throughput or high-content (high-context) assay formats is described for a diversity of reporters, with particular detail provided for examples of monomeric enzymes and fluorescent proteins.

Abstract: We describe a strategy for designing and implementing protein-fragment complementation assays (PCAs) to detect biomolecular interactions in vivo and in vitro. The design, implementation and broad applications of this strategy are illustrated with a large number of enzymes with particular detail provided for the example of murine dihydrofolate reductase (DHFR). Fusion peptides consisting of N- and C-terminal fragments of murine DHFR fused to GCN4 leucine zipper sequences were coexpressed in Escherichia coli grown in minimal medium, where the endogenous DHFR activity was inhibited with trimethoprim. Coexpression of the complementary fusion products restored colony formation. Survival only occurred when both DHFR fragments were present and contained leucine-zipper forming sequences, demonstrating that reconstitution of enzyme activity requires assistance of leucine zipper formation. DHFR fragment-interface point mutants of increasing severity (Ile to Val, Ala and Gly) resulted in a sequential increase in E.

Abstract: The present invention is directed to Protein-fragment Complementation Assays (PCAs) and assay compositions based on fluorescent proteins. The invention provides methods for fragmenting fluorescent proteins and generating mutant fragments with desired spectral characteristics for PCA. The invention encompasses assays and compositions based on fluorescent proteins from the species Aequorea, Anemonia and Anthozoa. In particular, the invention is directed to fragments of mutant fluorescent proteins having improved spectral properties over the wild-type proteins. The invention encompasses fragments of mutant versions of A. Victoria green fluorescent protein (GFP), in particular yellow fluorescent proteins (EYFP and super-EYFP), ‘Venus’, cyan, ‘citrine’, blue, cyan-green, and photoactivatable variants of GFP The invention also encompasses red fluorescent PCAs based on Discosoma red fluorescent protein (RFP PCA) and a kindling fluorescent protein PCA (KFP1 PCA) derived from Anemonia sulcata.

Abstract: The present invention provides functional annotation of novel genes by detection of interactions of their encoded proteins with known proteins followed by assays to validate that the gene participates in a specific cellular function. The instant invention also provides an experimental strategy that allows for detection of protein interactions and functional assays with a single reporter system. Interactions among network component proteins are detected and probed with stimulators and inhibitors of the network and subcellular location of the interacting proteins is determined. Additionally, applicants' use this strategy to map a signal transduction network that controls the G0 to G1 transition in eukaryotes. Analysis of 148 combinations of 65 protein pairs in mammalian cells allows applicants' to propose a model of network architecture. The results demonstrate the feasibility of employing this strategy in genome-wide functional annotation efforts.

Abstract: The present invention describes a method for detecting biomolecular interactions said method comprising: (a) selecting an appropriate reporter molecule selected from the group consisting of a protein, a fluorescent protein, a luminescent protein and a phosphorescent protein; (b) effecting fragmentation of said reporter molecule such that said fragmentation results in reversible loss of reporter function; (c) fusing or attaching fragments of said reporter molecule separately to other molecules; followed by (d) reassociation of said reporter fragments through interactions of the molecules that are fused to said fragments; and (e) detecting said biomolecular interactions by reconstitution of activity of the reporter molecule.

Abstract: The present invention describes an assay method comprising: (A) generating (1) at least a first fragment of a reporter molecule linked to a first interacting domain and at least a second fragment of a reporter molecule linked to a second interacting domain, or (2) nucleic acid molecules that code for (A)(1) and subsequently allowing said nucleic acid molecules to produce their coded products; then, (B) allowing interaction of said domains; and (C) detecting reconstituted reporter molecule activity, where said reporter molecule can react with a penicillin- or a cephalosporin-class substrate.

Abstract: The present invention provides protein fragment complementation assays for drug discovery, in particular to identify compounds that activate or inhibit cellular pathways. Based on the selection of an interacting protein pair combined with an appropriate PCA reporter, the assays may be run in high-throughput or high-content mode and may be used in automated screening of libraries of compounds. The interacting pair may be selected by cDNA library screening; by gene-by-gene interaction mapping; or by prior knowledge of a pathway. Fluorescent and luminescent assays can be constructed using the methods provided herein. The selection of suitable PCA reporters for high-throughput or high-content (high-context) assay formats is described for a diversity of reporters, with particular detail provided for examples of monomeric enzymes and fluorescent proteins.

Abstract: The present invention describes rapid methods to screen for biomolecular interactions in vivo based on protein fragment complementation assays (PCA). We have demonstrated an in vivo library-versus-library screening strategy that has numerous applications in the identification of novel protein-protein interactions and in directed evolution. Also we demonstrate the detection of protein-protein interactions starting with defined (full-length) cDNAs, and the concomitant generation of functional assays that provide initial validation of the cDNA products as being biologically relevant. Also, we screened a large cDNA collection using automated PCA, combined with quantitative detection of protein-protein complexes. The invention enables bait-vs.-library, library-vs.-library and defined gene screening in any type of cell or cellular context, and using a wide range of reporters and detection methods.

Abstract: A method of assaying protein-protein interactions associated with proteins involved in lipid pathways using a protein fragment complementation assays, said method comprising the steps of: (a) identifying protein molecules that interact with said protein associated with lipid pathways; (b) selecting a protein reporter molecule; (c) effecting fragmentation of said protein reporter molecule such that said fragmentation results in reversible loss of reporter function; (d) fusing or attaching fragments of said protein reporter molecule separately to said interacting protein molecules as defined in step (a); (e) transfecting cells with nucleic acid constructs coding for the products of step (d); (f) reassociating said reporter fragments through interactions of the protein molecules that are fused or attached to said fragments; and (g) measuring directly or Indirectly the activity of said reporter molecule resulting from the reassociation of said reporter fragments.

Abstract: The present invention describes a rapid and efficient in vivo library-versus-library screening strategy for identifying optimally interacting pairs of heterodimerizing polypeptides. It allows for the screening of a protein library against a second protein library, rather than against a single bait protein, and thus has numerous applications in the study of protein-protein interactions. Additionally, it allows for the application of different selection stringencies. Two leucine zipper libraries, semi-randomized at the positions adjacent to the hydrophobic core, were genetically fused to either one of two designed fragments of the enzyme murine dihydrofolate reductase (mDHFR), and cotransformed into E. coli. Interaction between the library polypeptides was required for reconstitution of the enzymatic activity of mDHFR, allowing bacterial growth.

Abstract: The present invention describes a rapid and efficient in vivo library-versus-library screening strategy for identifying optimally interacting pairs of heterodimerizing polypeptides. It allows for the screening of a protein library against a second protein library and therefore finds numerous applications in the study of protein-protein interactions. Two leucine zipper libraries, semi-randomized at the positions adjacent to the hydrophobic core, were genetically fused to either one of two designed fragments of the enzyme murine dihydrofolate reductase (mDHFR), and cotransformed into E. coli. Interaction between the library polypeptides was required for reconstitution of the enzymatic activity of mDHFR, allowing bacterial growth. Using more weakly associating mDHFR fragments, we increased the stringency of selection. We applied these selection processes to a library-versus-library sample of 2.

Abstract: The invention provides a method of screening a candidate drug, a compound library or a biological extract to identify activators or inhibitors of G-protein-coupled receptors or G-protein-coupled pathways, comprising: (A) using a fluorescent protein fragment complementation assay to construct an assay for one or more steps in a G-protein-coupled pathway; (B) testing the effects of the candidate drugs, compound library, or biological extract on the receptor or pathway of interest; and (C) using the results of the screening to identify specific agents that activate or inhibit the receptor or pathway of interest. The invention also provides a method for identifying a drug lead that modulates the activity of a G-protein-coupled pathway using a fluorescent protein fragment complementation assay. The method of the invention is used to identify agonists, antagonists, activators or inhibitors of G-protein coupled receptors or G-protein-coupled pathways.

Abstract: The cell-based assays described in the present invention can be used to directly assess the sensitivity and specificity of the gene annotation reagent against its target, and to determine if a non-targeted gene participates in a pathway of interest or is functionally linked to another gene or protein. The combination of annotation reagents with such cell-based assays is useful for mapping genes (proteins) into cellular pathways on a genome-wide scale. Preferred assay embodiments include fluorescence or luminescence assays in intact (live or fixed) cells. Such fluorescence or luminescence assays include high-throughput or high-content assays for protein activity, subcellular localization, post-translational modifications, or interactions of proteins. Suitable assays may include protein-protein interaction assays; protein translocation assays; and post-translational modification assays.

Abstract: The instant invention describes a method for detecting protein-protein interactions in living organisms and/or cells, said method comprising: (a) synthesizing probe protein fragments from a protein which enables fluorescent or luminescent detection by dissecting the gene coding for the fluorescent or luminescent protein into a least two fragments; (2) constructing fusion proteins consisting of the probe protein fragments linked to protein domains that are to be tested for interactions; (3) coexpressing the fusion proteins; and (d) detecting reconstitution of the fluorescence or luminescence signal.

Abstract: This invention provides principles, methods and compositions for ascertaining the mechanism of action of pharmacologically important compounds in the context of network biology, across the entire scope of the complex pathways of living cells. Importantly, the principles, methods and compositions provided allow a rapid assessment of the on-pathway and off-pathway effects of lead compounds and drug candidates in living cells, and comparisons of lead compounds with well-characterized drugs and toxicants to identify patterns associated with efficacy and toxicity. The invention will be useful in improving the drug discovery process, in particular by identifying drug leads with desired safety and efficacy and in effecting early attrition of compounds with potential adverse effects in man.

Abstract: The present invention is directed to Protein-fragment Complementation Assays (PCAs) and assay compositions based on fluorescent proteins. The invention provides methods for fragmenting fluorescent proteins and generating mutant fragments with desired spectral characteristics for PCA. The invention encompasses assays and compositions based on fluorescent proteins from the species Aequorea, Anemonia and Anthozoa. In particular, the invention is directed to fragments of mutant fluorescent proteins having improved spectral properties over the wild-type proteins. The invention encompasses fragments of mutant versions of A. Victoria green fluorescent protein (GFP), in particular yellow fluorescent proteins (EYFP and super-EYFP), ‘Venus’, cyan, ‘citrine’, blue, cyan-green, and photoactivatable variants of GFP.

Abstract: The present invention describes a method for detecting biomolecular interactions said method comprising: (a) selecting an appropriate reporter molecule selected from the group consisting of a protein, a fluorescent protein, a luminescent protein and a phosphorescent protein; (b) effecting fragmentation of said reporter molecule such that said fragmentation results in reversible loss of reporter function; (c) fusing or attaching fragments of said reporter molecule separately to other molecules; followed by (d) reassociation of said reporter fragments through interactions of the molecules that are fused to said fragments; and (e) detecting said biomolecular interactions by reconstitution of activity of the reporter molecule.

Abstract: The present invention provides protein fragment complementation assays for drug discovery, in particular to identify compounds that activate or inhibit cellular pathways. Based on the selection of an interacting protein pair combined with an appropriate PCA reporter, the assays may be run in high-throughput or high-content mode and may be used in automated screening of libraries of compounds. The interacting pair may be selected by cDNA library screening; by gene-by-gene interaction mapping; or by prior knowledge of a pathway. Fluorescent and luminescent assays can be constructed using the methods provided herein. The selection of suitable PCA reporters for high-throughput or high-content (high-context) assay formats is described for a diversity of reporters, with particular detail provided for examples of monomeric enzymes and fluorescent proteins.

Abstract: This invention provides principles, methods and compositions for ascertaining the mechanism of action of pharmacologically important compounds in the context of network biology, across the entire scope of the complex pathways of living cells. Importantly, the principles, methods and compositions provided allow a rapid assessment of the on-pathway and off-pathway effects of lead compounds and drug candidates in living cells, and comparisons of lead compounds with well-characterized drugs and toxicants to identify patterns associated with efficacy and toxicity. The invention will be useful in improving the drug discovery process, in particular by identifying drug leads with desired safety and efficacy and in effecting early attrition of compounds with potential adverse effects in man.