A live cell protein complementation assay for ORFeome-wide probing of human HOX interactomes

Biological pathways rely on the formation of intricate protein interaction networks called interactomes. Getting a comprehensive map of interactomes implies developing tools that allow capturing transient and low affinity protein-protein interactions (PPIs) in live conditions. Here we present an experimental strategy, Cell-PCA (Cell Protein Complementation Assay), which is based on BiFC (Bimolecular Fluorescence Complementation) and high throughput sequencing for ORFeome-wide analyses of different interactomes in the same live cell context. The specificity and sensitivity of Cell-PCA was established by using a wild type and a single amino-acid mutated HOXA9 protein, and the approach was subsequently applied for seven additional human HOX proteins. These proof-of-concept experiments revealed novel molecular properties of HOX interactomes and led to the identification of a novel cofactor of HOXB13 for promoting its proliferative activity in a cancer cell context. Taken together, our work demonstrates that Cell-PCA is pertinent for revealing and, importantly, comparing interactomes between different or highly related bait proteins in the same cell context.