A repackaged CRISPR platform increases homology-directed repair for yeast engineering

Abstract

Inefficient homology-directed repair (HDR) constrains CRISPR–Cas9 genome editing in organisms that preferentially employ nonhomologous end joining (NHEJ) to fix DNA double-strand breaks (DSBs). Current strategies used to alleviate NHEJ proficiency involve NHEJ disruption. To confer precision editing without NHEJ disruption, we identified the shortcomings of the conventional CRISPR platforms and developed a CRISPR platform—lowered indel nuclease system enabling accurate repair (LINEAR)—which enhanced HDR rates (to 67–100%) compared to those in previous reports using conventional platforms in four NHEJ-proficient yeasts. With NHEJ preserved, we demonstrate its ability to survey genomic landscapes, identifying loci whose spatiotemporal genomic architectures yield favorable expression dynamics for heterologous pathways. We present a case study that deploys LINEAR precision editing and NHEJ-mediated random integration to rapidly engineer and optimize a microbial factory to produce (S)-norcoclaurine. Taken together, this work demonstrates how to leverage an antagonizing pair of DNA DSB repair pathways to expand the current collection of microbial factories.

CRISPR–Cas9 genome editing is limited in organisms with inefficient homology-directed repair (HDR), but development of a specialized CRISPR platform conferred increased HDR rates in four noncanonical yeasts to enhance strain engineering.