A plasmid DNA primase active in discontinuous bacterial DNA replication

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• DNA replication requires a primase enzyme to synthesize RNA primers.
• Escherichia coli primase is essential for chromosomal DNA replication.
• Plasmids can carry genes that complement host deficiencies.

Purpose of the Study:

• To investigate the function of a DNA primase encoded by an IncI alpha plasmid.
• To determine if the plasmid primase can support DNA replication in a primase-deficient host.

Main Methods:

• Complementation assay using a primase-defective mutant of Escherichia coli.
• Analysis of DNA replication and synthesis.

Main Results:

• The IncI alpha plasmid primase efficiently complemented the primase defect in Escherichia coli.
• The plasmid enzyme facilitated DNA replication in the mutant host.
• The plasmid gene encodes two large, antigenically related proteins distinct from E. coli primase.

Conclusions:

• The IncI alpha plasmid primase can prime discontinuous DNA synthesis of the bacterial chromosome.
• Plasmid-encoded primases represent a potential alternative for initiating DNA replication.