Print Email Facebook Twitter PAM-repeat associations and spacer selection preferences in single and co-occurring CRISPR-Cas systems Title PAM-repeat associations and spacer selection preferences in single and co-occurring CRISPR-Cas systems Author Vink, J.N.A. (TU Delft BN/Stan Brouns Lab; Kavli institute of nanoscience Delft) Baijens, J.H.L. (TU Delft BN/Stan Brouns Lab; Kavli institute of nanoscience Delft) Brouns, S.J.J. (TU Delft BN/Stan Brouns Lab; Kavli institute of nanoscience Delft) Date 2021 Abstract Background: The adaptive CRISPR-Cas immune system stores sequences from past invaders as spacers in CRISPR arrays and thereby provides direct evidence that links invaders to hosts. Mapping CRISPR spacers has revealed many aspects of CRISPR-Cas biology, including target requirements such as the protospacer adjacent motif (PAM). However, studies have so far been limited by a low number of mapped spacers in the database. Results: By using vast metagenomic sequence databases, we map approximately one-third of more than 200,000 unique CRISPR spacers from a variety of microbes and derive a catalog of more than two hundred unique PAM sequences associated with specific CRISPR-Cas subtypes. These PAMs are further used to correctly assign the orientation of CRISPR arrays, revealing conserved patterns between the last nucleotides of the CRISPR repeat and PAM. We could also deduce CRISPR-Cas subtype-specific preferences for targeting either template or coding strand of open reading frames. While some DNA-targeting systems (type I-E and type II systems) prefer the template strand and avoid mRNA, other DNA- and RNA-targeting systems (types I-A and I-B and type III systems) prefer the coding strand and mRNA. In addition, we find large-scale evidence that both CRISPR-Cas adaptation machinery and CRISPR arrays are shared between different CRISPR-Cas systems. This could lead to simultaneous DNA and RNA targeting of invaders, which may be effective at combating mobile genetic invaders. Conclusions: This study has broad implications for our understanding of how CRISPR-Cas systems work in a wide range of organisms for which only the genome sequence is known. To reference this document use: http://resolver.tudelft.nl/uuid:ae10e1df-3ac5-4710-bea3-787c9e909dba DOI https://doi.org/10.1186/s13059-021-02495-9 ISSN 1474-7596 Source Genome Biology (Online), 22 (1) Part of collection Institutional Repository Document type journal article Rights © 2021 J.N.A. Vink, J.H.L. Baijens, S.J.J. Brouns Files PDF s13059_021_02495_9.pdf 1.43 MB Close viewer /islandora/object/uuid:ae10e1df-3ac5-4710-bea3-787c9e909dba/datastream/OBJ/view