Making the cut with PAMless CRISPR-Cas enzymes

Genome editing technologies simplify our ability to rewrite genetic blueprints of life. However, CRISPR-Cas enzymes found in nature can only manipulate a fraction of the genome. To overcome this limitation, new Cas variants have been developed that unlock nearly the entire genome for editing. Genome editing technologies simplify our ability to rewrite genetic blueprints of life. However, CRISPR-Cas enzymes found in nature can only manipulate a fraction of the genome. To overcome this limitation, new Cas variants have been developed that unlock nearly the entire genome for editing. modified versions of Cas enzymes that harbor fusions to deaminase domains, permitting the directed conversion of DNA or RNA bases. Cas enzymes, encoded by CRISPR systems, are an essential component of CRISPR immune systems that protect bacteria and archaea from invading nucleic acids. They can be reprogrammed via a gRNA to bind and cleave DNA targets. a short RNA molecule that directs Cas enzymes to target sites. The gRNA can be comprised of a single crRNA or a dual crRNA with tracrRNA, that together can be joined to form a single composite gRNA. Complementarity between the spacer of the gRNA and the protospacer of the target site is required for DNA or RNA binding. a genome editing technology built on the Cas enzyme chassis that contains a fusion to a reverse transcriptase domain, which enables the introduction of insertions, deletions, and base conversions. a short DNA sequence next to protospacers of DNA targets, which permits most Cas enzymes to proofread invading DNA segments (distinguishing 'self' DNA from foreign and potentially pathogenic nucleic acids).