Episomal editing of synthetic constructs in yeast using CRISPR

Use of synthetic genomics to design and build "big" DNA has revolutionized our ability to answer fundamental biological questions by employing a bottom-up approach. S. cerevisiae, or budding yeast, has become the major platform to assemble large synthetic constructs thanks to its powerful homologous recombination machinery and the availability of well-established molecular biology techniques. However, efficiently and precisely introducing designer variations to episomal assemblies remains challenging. Here, we describe CRISPR Engineering of EPisomes in Yeast, or CREEPY, for rapid engineering of mammalian DNA constructs larger than 100 kb. We demonstrate that editing of circular episomes presents unique challenges compared to modifying native yeast chromosomes with CRISPR. After optimizing CREEPY for episomal editing, we achieve efficient simplex and multiplex editing as demonstrated by engineering a mouse Sox2-harboring episome.