A novel high-throughput functional screen based upon chimeric minimotif decoys

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DESCRIPTION (provided by applicant): Scientists are trying to understand cells and humans as a system by developing high- throughput technologies and modeling large networks of metabolites, transcriptional responses, protein-protein interactions, genetic interactions, etc. These technologies create orthogonal knowledge that can be integrated to provide a systemic model of the cell and organism. Currently, a disconnect exists in the knowledge gained from high-throughput screens regarding protein function. RNAi screens used to identify genes that are required for a cell process are often coupled with knowledge of molecular pathways to construct pathways and networks in the cell required for a cell process. However, there is no high-throughput technology to experimentally identify the molecular functions that mediate these gene interactions, which are commonly inferred in many papers. Here, we propose to develop and test a novel chimeric minimotif decoy (CMD) screen that identifies the roles of different molecular functions in assayable cell processes. This screen is based upon our Minimotif Miner database of ~600,000 short functional peptide sequences with an experimentally determined molecular function. In this screen, an expression plasmid library is generated from chimera of random subsets of minimotifs appended in-frame to the end of a red fluorescent protein cDNA. Individual clones are transfected in separate wells of a multiwell plate and scored in any type of high-throughput assay. Positive clones are sequenced and related back to the Minimotif Miner database to identify molecular functions involved in assayed process. In our proof of principle experiments, we tested this approach on a fluorogenic HIV infection assay. We built and screened a plasmid library containing minimotifs that are required for HIV infection and demonstrated that we could rediscover some minimotifs as inhibiting HIV infection, providing proof of principle for this approach. The HIV infection assay provides an excellent system to develop and evaluate the CMD screening technology. There are well-established high-throughput fluorescent HIV infection assays, HIV exploits the use of minimotifs, a HIV minimotif (Enfurvirtide) is an FDA approved drug, and interpretation of results is facilitated by abundant information concerning HIV infection. Here, in aim 1, we will optimize the CMD screen to rediscover minimotifs that block HIV infection. In aim 2, we will build a much larger library with broader diversity of minimotif functions and genes. The library will be screened for novel minimotifs that block HIV infection. For select novel minimotifs identified in the CMD screen, we will validate the identified minimotifs using siRNA and mutagenesis of the minimotif. At this early stage of development of the CMD technology we envision four immediate potential uses. The CMD screen will: (1) provide an independent approach to validate HIV infection host dependency factors (HDFs) identified in RNAi screens; (2) experimentally identify the molecular basis of functional interactions between some host dependency factors; (3) identify novel host dependency factors; and (4) identify combinations of different sets of minimotifs that, together block HIV infection will be identified.