Dual-origin plasmid vectors whose origin of replication is controlled by the coliphage lambda promoter pL

Area of Science:

• Molecular Biology
• Plasmid Engineering
• Gene Expression Systems

Background:

• The ColE1 plasmid origin of replication is crucial for controlling DNA replication.
• Modifying this origin can lead to improved plasmid stability and expression control.
• Controllable promoters offer advantages for regulated gene expression.

Purpose of the Study:

• To engineer a modified ColE1 origin of replication for enhanced control.
• To develop stable and amplifiable dual-origin plasmids.
• To facilitate the construction of versatile expression vectors.

Main Methods:

• Insertion of an XhoI linker near the 5' end of the RNA II primer.
• Replacement of the natural RNA II promoter with controllable promoters (e.g., lambda pL).
• Construction of dual-origin plasmids utilizing pSC101 for stable maintenance.

Main Results:

• Successfully replaced the native RNA II promoter with controllable alternatives.
• Demonstrated stable maintenance of dual-origin plasmids at ~4 copies per chromosome at 30°C.
• Achieved efficient plasmid amplification via thermal induction using a thermolabile lambda repressor.

Conclusions:

• The modified origin enables precise control over plasmid replication and gene expression.
• Dual-origin plasmids provide a stable and amplifiable platform for expression vectors.
• This system is suitable for constructing advanced, controllable gene expression systems.