Deletion during recombination in bacteriophage T7

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• Bacteriophage T7 ligase gene function is crucial for viral replication.
• Genetic recombination mechanisms can lead to deletions within viral genomes.
• Understanding deletion mutagenesis is key to comprehending genome stability.

Purpose of the Study:

• To investigate the role of intermolecular recombination in deleting inserts within the T7 ligase gene.
• To compare deletion frequencies based on the proximity and arrangement of repeated DNA sequences.
• To explore the potential involvement of sequence misalignment in T7 deletion mutagenesis.

Main Methods:

• Synthetic DNA inserts containing identical 17 bp repeats were introduced into the T7 ligase gene.
• Deletion frequencies were measured for repeats located on separate genomes versus the same genome.
• Deletion frequencies were compared for repeats separated by 39 bp versus adjacent repeats.

Main Results:

• Intermolecular recombination between separate T7 genomes resulted in functional ligase gene formation at 7-13% of the frequency observed with repeats on the same genome.
• Deletion frequency was significantly higher (two orders of magnitude) when repeats were adjacent compared to when separated by 39 bp.
• The presence of non-homologous sequence (39 bp) between repeats reduced deletion frequency.

Conclusions:

• Intermolecular recombination is an effective mechanism for deleting genetic material in bacteriophage T7.
• Sequence misalignment between repeated elements during intermolecular recombination likely contributes to deletion mutagenesis in T7.
• The spatial arrangement of homologous sequences significantly influences deletion rates.