Efficient assembly of a synthetic attenuated SARS-CoV-2 genome in Saccharomyces cerevisiae using multi-copy yeast vectors

Abstract

Saccharomyces cerevisiae has been demonstrated to be an excellent platform for the multi-fragment assembly of large DNA constructs through its powerful homologous recombination ability. These assemblies have invariably used the stable centromeric single copy vectors. However, many applications of these assembled genomes would benefit from assembly in a higher copy number vector for improved downstream extraction of intact genomes from the yeast. A review of the literature revealed that large multi-fragment assemblies did not appear to have been attempted in multicopy vectors. Therefore, we devised a toolkit that would enable one to seamlessly transition with the same assembling fragments between a single copy and a multicopy vector. We evaluated the assembly of a 28 kb attenuated SARS-CoV-2 genome (lacking the N gene) from 10 fragments in both single copy and multicopy vector systems. Our results reveal that assembly was comparably efficient in the two vector systems. The findings should add to the synthetic biology toolkit of S. cerevisiae and should enable researchers to utilize any of these vector systems depending on their downstream applications.