FIGURE 1: Complementary yeast-based technologies to probe SARS-CoV-2 biology. Top: Synthetic Protein Interaction (SPI) technology by Klemm et al allows unbiased identification of toxic viral-eukaryotic protein interactions in yeast. Haploid yeast cells expressing a SARS-CoV-2 protein fused to a high affinity GFP binding protein (GPB) are mated to the yeast GFP strain library. Upon expression of the SARS-CoV2-GBP chimera, SPIs are identified as yeast strains having a growth defect due to the forced interaction of the viral query protein with the yeast target protein. Bottom right: Directed evolution and yeast display as described by Zahradník et al generates SARS-CoV-2 proteins with enhanced binding properties or activities. A library of protein variants (spike protein, for example) generated by random mutagenesis is displayed on the yeast cell surface. Variants that exhibit improved binding or activity are identified and sorted by flow cytometry, and used to prepare a new variant library. The cycle is repeated until variants with the desired properties are identified. Bottom left: Viral genome assembly in yeast as described by Thao et al allows rapid SARS-CoV-2 genome reconstruction and engineering to study viral gene functions. Segments of the SARS-CoV-2 genome are generated via gene synthesis or RT-PCR from patient samples and assembled into a plasmid via recombination in yeast. Upon plasmid recovery, viral RNA is synthesized in vitro and electroporated into human cell lines to generate functional viral particles for analysis of virus replication and other viral functions.