Shotgun knockdown of RNA by CRISPR-Cas13d in fission yeast

Arrayed CRISPRi library to suppress genes required for Schizosaccharomyces pombe viability

The fission yeast, Schizosaccharomyces pombe, is an excellent eukaryote model organism for studying essential biological processes. Its genome contains ∼1,200 genes essential for cell viability, most of which are evolutionarily conserved. To study these essential genes, resources enabling conditional perturbation of target genes are required. Here, we constructed comprehensive arrayed libraries of plasmids and strains to knock down essential genes in S. pombe using dCas9-mediated CRISPRi. These libraries cover ∼98% of all essential genes in fission yeast. We estimate that in ∼60% of these strains, transcription of a target gene was repressed so efficiently that cell proliferation was significantly inhibited. To demonstrate the usefulness of these libraries, we performed metabolic analyses with knockdown strains and revealed flexible interaction among metabolic pathways. Libraries established in this study enable comprehensive functional analyses of essential genes in S. pombe and will facilitate the understanding of essential biological processes in eukaryotes.

On the ever-growing functional versatility of the CRISPR-Cas13 system

CRISPR-Cas systems evolved in prokaryotes to implement a powerful antiviral immune response as a result of sequence-specific targeting by ribonucleoproteins. One of such systems consists of an RNA-guided RNA endonuclease, known as CRISPR-Cas13. In very recent years, this system is being repurposed in different ways in order to decipher and engineer gene expression programmes. Here, we discuss the functional versatility of the CRISPR-Cas13 system, which includes the ability for RNA silencing, RNA editing, RNA tracking, nucleic acid detection and translation regulation. This functional palette makes the CRISPR-Cas13 system a relevant tool in the broad field of systems and synthetic biology.

Transcriptional Regulation Technology for Gene Perturbation in Fission Yeast

Isolation and introduction of genetic mutations is the primary approach to characterize gene functions in model yeasts. Although this approach has proven very powerful, it is not applicable to all genes in these organisms. For example, introducing defective mutations into essential genes causes lethality upon loss of function. To circumvent this difficulty, conditional and partial repression of target transcription is possible. While transcriptional regulation techniques, such as promoter replacement and 3' untranslated region (3'UTR) disruption, are available for yeast systems, CRISPR-Cas-based technologies have provided additional options. This review summarizes these gene perturbation technologies, including recent advances in methods based on CRISPR-Cas systems for Schizosaccharomyces pombe. We discuss how biological resources afforded by CRISPRi can promote fission yeast genetics.