Abstract: Provided herein are methods of disrupting DNA substrates in eukaryotic cells and methods of introducing exogenous polynucleotides into target sites in the DNA substrates In certain embodiments the methods comprise introducing a purified group II intron ribonucleoprotein (RNP) particle into the host cell. In certain embodiments the method comprises introducing a group II intron RNP particle and a DNA construct comprising an exogenous polynucleotide flanked by sequences that are homologous to sequences that flank the target site in the endogenous DNA substrate. In certain embodiments, the methods also involve introducing magnesium ions into the eukaryotic cells.