Preparing Fosmid Mate-Paired Libraries Using Cre-LoxP Recombination

Area of Science:

• Genomics
• Molecular Biology
• Bioinformatics

Background:

• Fosmid end sequencing is crucial for genome assembly and structural variation studies.
• Existing methods for constructing fosmid paired-end libraries have limitations for certain sequencing platforms.

Purpose of the Study:

• To develop an improved method for constructing fosmid paired-end libraries compatible with the Illumina sequencing platform.
• To enhance genome assembly and structural variation analysis through more efficient fosmid library construction.

Main Methods:

• A modified fosmid vector (pFosClip) with specific loxP sites and inverse Illumina adaptor priming sites was engineered.
• Cre recombinase treatment removed most vector DNA, leaving a short vector sequence with insert DNA.
• Restriction enzyme digestion, recircularization, and inverse PCR were employed to generate and enrich fosmid paired ends.

Main Results:

• The new method efficiently circularizes short DNA fragments, improving success rates compared to blunt-end ligation methods.
• Restriction enzyme digestion creates identifiable junction tags for splitting paired reads, aiding data analysis.
• The approach generated predominantly fosmid-sized (30-40 Kb) pairs from fungal and plant genomes, significantly increasing assembled scaffold sizes.

Conclusions:

• This novel fosmid paired-end library construction method is highly efficient and suitable for Illumina sequencing.
• The technique facilitates improved genome assembly and structural variation studies by producing larger scaffolds.
• The method offers advantages in fragment handling, read splitting, and overcoming enzyme-cutting bias.