Efficient Generation of Genome-wide Libraries for Protein-ligand Screens Using Gibson Assembly

Genome-wide screens using yeast or phage displays are powerful tools for identifying protein-ligand interactions, including drug or vaccine targets, ligand receptors, or protein-protein interactions. However, assembling libraries for genome-wide screens can be challenging and often requires unbiased cloning of 10 ⁵ -10 ⁷ DNA fragments for a complete representation of a eukaryote genome. A sub-optimal genomic library can miss key genomic sequences and thus result in biased screens. Here, we describe an efficient method to generate genome-wide libraries for yeast surface display using Gibson assembly. The protocol entails genome fragmentation, ligation of adapters, library cloning using Gibson assembly, library transformation, library DNA recovery, and a streamlined Oxford nanopore library sequencing procedure that covers the length of the cloned DNA fragments. We also describe a computational pipeline to analyze the library coverage of the genome and predict the proportion of expressed proteins. The method allows seamless library transfer among multiple vectors and can be easily adapted to any expression system.