Response to Comment on "RNA-guided DNA insertion with CRISPR-associated transposases"

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• The CRISPR-associated transposase ShCAST system offers a novel method for targeted DNA insertion.
• Previous research suggested potential for complex insertion products beyond simple DNA integration with ShCAST.
• Understanding the precise outcomes of ShCAST-mediated insertions is crucial for its effective application.

Purpose of the Study:

• To elucidate the specific outcomes of ShCAST-mediated DNA insertions in *Escherichia coli*.
• To investigate whether ShCAST leads to simple insertions or integration of the entire donor plasmid.
• To identify strategies for controlling ShCAST insertion products.

Main Methods:

• Utilized the CRISPR-associated transposase ShCAST system for DNA insertions in *Escherichia coli*.
• Employed both standard and 5' nicked DNA donors to assess their impact on insertion outcomes.
• Analyzed the resulting DNA products to differentiate between simple integration and donor plasmid integration.

Main Results:

• ShCAST-mediated insertions in *Escherichia coli* resulted in both simple integration of the target DNA and integration of the entire donor plasmid.
• The integration of the donor plasmid represents an unintended and potentially problematic outcome.
• Using a 5' nicked DNA donor effectively prevented the integration of the donor plasmid.

Conclusions:

• The ShCAST system can mediate both desired simple insertions and undesired donor plasmid integration in *E. coli*.
• The use of a 5' nicked DNA donor is a viable strategy to exclusively achieve simple insertions.
• This finding refines the understanding of ShCAST system mechanics and enhances its utility in genetic engineering applications.