Abstract

Argonaute (Ago) proteins are programmable nuclease found in both eukaryotes and prokaryotes. Prokaryotic Argonaute proteins (pAgos) share a high degree of structural homology with eukaryotic Argonaute proteins (eAgos) and eAgos are considered to evolve from pAgos. However, the majority of studied pAgos prefer to cleave DNA targets, and eAgos exclusively cleave RNA targets. Here, we characterize a novel pAgo, MbpAgo, from psychrotolerant bacteria Mucilaginibacter paludis that can be programmed with DNA guides and prefers to cleave RNA targets rather than DNA targets. MbpAgo can be active at a wide range of temperatures (4-65{degrees}C). In comparison with previously studied pAgos, MbpAgo is able to utilize 16-nt long 5phosphorylated and 5hydroxylated DNA guides for efficient and precise cleavage and displays no obvious preference for the 5end nucleotide of a guide. Furthermore, the cleavage efficiency can be regulated by mismatches in the central and 3supplementary regions of the guide. MbpAgo can efficiently cleave highly-structured RNA targets using both 5phosphorylated and 5hydroxylated DNA guides in the presence of Mg2+ or Mn2+. In conclusion, we have demonstrated that MbpAgo is a unique programmable nuclease that has a strong preference for RNA targets, with great potential applications in the field of nucleic acid biotechnology.