System and method for genome editing

A genome editing system for site-directed modification of a target sequence in the genome of a cell, comprising at least one of the following i) to v):

• i) a C2c1 protein or variant thereof, and a guide RNA;
• ii) an expression construct comprising a nucleotide sequence encoding a C2c1 protein or variant thereof, and a guide RNA;
• iii) a C2c1 protein or variant thereof, and an expression construct comprising a nucleotide sequence encoding a guide RNA;
• iv) an expression construct comprising a nucleotide sequence encoding a C2c1 protein or variant thereof, and an expression construct comprising a nucleotide sequence encoding a guide RNA;
• v) an expression construct comprising a nucleotide sequence encoding a C2c1 protein or variant thereof and a nucleotide sequence encoding a guide RNA;
• wherein the guide RNA is capable of forming a complex with the C2c1 protein or variant thereof and targeting the C2c1 protein or variant thereof to the target sequence in the genome of the cell, resulting in substitution, deletion and/or addition of one or more nucleotides in the target sequence, wherein the C2c1 protein is a AaC2c1 protein derived from Alicyclobacillus acidiphilus,
• wherein
• 1) the AaC2c1 protein comprises an amino acid sequence set forth in SEQ ID NO:1, and the guide RNA is a sgRNA;
• or
• 2) the variant of the AaC2c1 protein comprises an amino acid sequence having at least 95% but less than 100% sequence identity to SEQ ID NO:
• 1, and has the RNA-mediated DNA binding activity and/or DNA cleavage activity of the AaC2c1 protein comprising an amino acid sequence set forth in SEQ ID NO:1.