Interactions between the RepB initiator protein of plasmid pMV158 and two distant DNA regions within the origin of...

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Rolling circle replication is a common DNA replication mechanism.
• Plasmids typically have one initiator protein binding site at the replication origin.
• The pMV158 plasmid's origin of replication exhibits an unusual dual binding site.

Purpose of the Study:

• To investigate the unique dual binding sites of the pMV158 plasmid's replication origin.
• To characterize the interaction between the initiator protein RepB and these binding sites.
• To elucidate the mechanism by which these interactions facilitate rolling circle replication.

Main Methods:

• High-resolution DNA footprinting assays were employed.
• The binding affinity and stability of RepB to different DNA loci were assessed.
• The structural changes induced by RepB binding to supercoiled DNA were analyzed.

Main Results:

• The pMV158 origin possesses two distinct RepB binding regions: the nic locus and a downstream bind locus.
• RepB exhibits higher affinity and stability for the bind locus compared to the nic locus.
• RepB binding induces DNA distortion and bending at the bind locus, and promotes hairpin formation at the nick site on supercoiled DNA.

Conclusions:

• The two RepB binding sites on the pMV158 origin interact cooperatively.
• This interplay facilitates initiator protein loading and proper DNA configuration for replication initiation.
• The findings provide insights into the regulation of rolling circle replication.