Chimeric DNA byproducts in strand displacement amplification using the T7 replisome

Area of Science:

• Molecular Biology
• Biochemistry
• Genomics

Background:

• Next-generation sequencing demands methods for amplifying long DNA molecules.
• In vivo DNA replication utilizes complex replisomes, not single enzymes.
• Strand-displacement amplification is a promising isothermal method for DNA synthesis.

Purpose of the Study:

• To investigate the T7 replisome's capability for producing long DNA amplicons.
• To understand the mechanism of T7 replisome-mediated strand-displacement amplification.
• To identify factors influencing amplicon generation for long DNA sequencing.

Main Methods:

• Utilized the T7 replisome (helicase, single-stranded DNA binding protein, DNA polymerase) for DNA amplification.
• Employed nicking endonucleases to initiate DNA synthesis on a 48 kb linear double-stranded DNA substrate.
• Analyzed amplified DNA products using Oxford Nanopore long-read sequencing technology.

Main Results:

• The T7 replisome successfully produced discrete DNA amplicons.
• Sequence analysis revealed chimeric DNA reads, indicating template switching.
• A link was established between template switching and polymerase exonuclease activity.

Conclusions:

• Oxford Nanopore sequencing offers insights into isothermal amplification of long DNA.
• High-specificity, high-turnover nicking endonucleases are crucial for initiating DNA amplification without thermal denaturation.
• Understanding replisome mechanisms can guide the development of advanced DNA amplification techniques.