A runaway-replication plasmid pSY343 contains two ssi signals.

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Plasmid pSY343 contains specific DNA segments with potential roles in replication.
• Single-stranded DNA (ssDNA) initiation signals are crucial for DNA replication processes.

Purpose of the Study:

• To identify and characterize single-stranded DNA initiation (ssi) signals within plasmid pSY343.
• To evaluate the impact of these ssi signals on phage vector replication and DNA conversion efficiency.

Main Methods:

• Plaque morphology method was used to detect ssi signals.
• ssi signals (ssiA and ssiB) were cloned into filamentous phage vectors (M13 delta lac184).
• Comparative analysis of chimera phage growth and ssDNA to replicative form (RF) DNA conversion efficiency.

Main Results:

• Two ssi signals, ssiA (170P) and ssiB (93F), were identified in plasmid pSY343.
• A conserved 7-nt consensus sequence was found within both ssi signals.
• Chimera phages M13 delta lac184/ssiA and M13 delta lac184/ssiB showed significantly increased growth (38- and 71-fold) and ssDNA to RF DNA conversion efficiency (1.9- and 2.2-fold).

Conclusions:

• ssiA and ssiB are functional single-stranded DNA initiation signals.
• These signals enhance phage vector replication and DNA conversion in vivo.
• The identified consensus sequence is likely involved in DNA priming on ssDNA templates.