Project description:We report the sites of protospacer integration into plasmids by Cas1-Cas2. The goal of this study is to determine the role of sequence elements on protospacer integration. Methods: Cas1-Cas2 integration products were fragmented, end-repaired, adapter ligated, PCR amplified, and analyzed by Illumina sequencing. Protospacer-containing reads were selected by Cutadapt and mapped to the plasmid with Bowtie.
Project description:We report the sites of protospacer integration into plasmids by Cas1-Cas2. The goal of this study is to determine the role of sequence elements on protospacer integration.
Project description:We report the integration site specificity of Cas1–Cas2 into target plasmid DNA encoding a CRISPR locus. The goal of this study is to determine the effect of IHF on target site selection of Cas1–Cas2.
Project description:Key to CRISPR-Cas adaptive immunity is maintaining an ongoing record of invading nucleic acids that are encountered, a process carried out by the Cas1-Cas2 complex that integrates short segments of foreign genetic material (spacers) into the CRISPR locus. It is hypothesized that Cas1 evolved from casposases, a novel class of transposases. We show here that casposase integration in vitro recapitulates several properties of CRISPR-Cas integrases. The X-ray structure of Methanosarcina mazei casposase bound to DNA representing the product of integration reveals a tetramer with target DNA bound snugly between two dimers in which single-stranded casposon end binding resembles that of spacer 3'-overhangs. The differences between transposase and CRISPR-Cas integrase are largely architectural, and it appears that evolutionary change involved changes in protein-protein interactions to favor Cas2 binding over tetramerization and the separation of Cas1 dimers. This, in turn, led to preferred integration of single spacers over two transposon ends.
Project description:Prokaryotic Cas1-Cas2 protein complexes generate adaptive immunity to mobile genetic elements (MGEs), by capture and integration of MGE DNA in to CRISPR sites. De novo immunity relies on Cas1-Cas2 targeting MGE DNA, without the aid of pre-existing immunity complexes, through mechanisms of ‘naive adaptation’ that are not clear. Using E. coli we show that the chaperone DnaK inhibits Cas1-Cas2 from DNA binding and integration, and that DnaK expression prevents naïve adaptation from chromosomal self-targeting. We show that that inhibition of naïve adaptation is reversible by eliminating DnaK from cells, by mutation of the DnaK substrate binding domain, and by expression of an MGE (phage )protein. We show that a fluorescently labelled Cas1 fusion can be visualised in living cells. Formation of foci depends on active DNA replication, and that the number of foci per cell is much increased in cells lacking DnaK. We discuss a model in which DnaK provides a mechanism for restraining naïve adaptation from self-targeting. This restraint is released once MGE DNA is present in the cell.
2023-05-18 | PXD042090 | Pride
Project description:Integration profiling of type V-C Cas1
