A new method for specific cleavage of megabase-size chromosomal DNA by lambda-terminase

Area of Science:

• Molecular Biology
• Genomics
• Biotechnology

Background:

• Physical mapping of large genomes requires methods for specific DNA cleavage at distant sites.
• Existing methods using restriction enzymes or intron-encoded endonucleases have limitations, including incomplete methylation and endogenous cleavage sites.
• The challenge lies in achieving precise and efficient cleavage of large DNA molecules.

Purpose of the Study:

• To develop a novel method for specific cleavage of intact chromosomal DNA.
• To utilize lambda-terminase for targeted DNA fragmentation.
• To assess the efficiency and specificity of this method for large genome mapping.

Main Methods:

• A plasmid with two lambda-terminase specific cleavage sites was introduced into *E. coli* and *S. cerevisiae* (yeast).
• Chromosomal DNA was isolated from engineered strains.
• Lambda-terminase was used to cleave the prepared chromosomal DNA.

Main Results:

• Specific cleavage of the 4.7-megabase pair (Mb) *E. coli* chromosome and the 0.58-Mb yeast chromosome V was achieved.
• Cleavage occurred at the intended sites with very high efficiencies.
• The lambda-terminase method demonstrated high specificity on intact chromosomal DNA.

Conclusions:

• Lambda-terminase provides a simple, one-step procedure for specific cleavage of large DNA molecules.
• This method is highly suitable for physical mapping of very large eukaryotic genomes.
• The approach overcomes limitations of existing DNA cleavage techniques.