Prokaryotic argonaute proteins and uses thereof

The invention relates to the field of genetic engineering tools, methods and techniques for nucleic acid, gene or genome editing. Specifically, the invention concerns prokaryotic Argonaute (pAgo) polypeptides having nuclease activity against target DNA when pAgo is complexed with a DNA guide. The invention also provides expression vectors comprising nucleic acids encoding said polypeptides as well as compositions and kits for, and methods of cleaving and editing target nucleic acids in a sequence-specific manner. The polypeptides, nucleic acids, expression vectors, compositions, kits and methods of the invention allow site- specific modifications of genetic material, whether isolated from cells in vitro, or within cells in situ and as such may usefully find application in many fields of biotechnology, including, for example, synthetic biology, gene therapy and agricultural or microbial biotechnology.