Mutational and in vivo methylation analysis of F-factor PifC protein binding to the pif operator and the region containing the primary origin of mini-F replication

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• The mini-F plasmid replication is regulated by the PifC protein.
• Understanding PifC's DNA-binding mechanism is crucial for elucidating replication control.

Purpose of the Study:

• To identify and characterize the in vivo DNA-binding sites of the mini-F replication factor PifC.
• To determine the structural features of the pif operator (pifO) and its interaction with PifC.

Main Methods:

• In vivo DNA-binding assays.
• Sequence analysis of constitutive mutants.
• Dimethyl sulfate methylation studies.

Main Results:

• Multiple DNA-binding sites for PifC were identified in vivo.
• The pifO operator contains a 17-bp region with dyad symmetry and perfect inverted repeats.
• PifC binding alters the reactivity of guanine residues within pifO.
• PifC-dependent methylation changes were observed upstream of pifO in homologous sequences.

Conclusions:

• PifC binds to specific DNA sequences, including the pifO operator, to regulate mini-F replication.
• The identified PifC binding sites and their relationship to oriV1 provide insights into replication control mechanisms.