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Dissecting the functional role of PriA protein-catalysed primosome assembly in Escherichia coli DNA replication
1Program in Molecular Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Insights
The PriA protein guides primosome assembly, crucial for DNA replication in E. coli. Studies suggest PriA-mediated primosome assembly contributes to normal chromosomal DNA replication.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The PriA protein is central to the primosome complex, essential for DNA replication initiation and elongation.
- Primosome assembly is vital for bacteriophage DNA synthesis and plasmid replication in vitro.
- The precise role of PriA-mediated primosome assembly in chromosomal replication remained unclear.
Purpose of the Study:
- To investigate the role of PriA-catalyzed primosome assembly in Escherichia coli chromosomal DNA replication.
- To elucidate the contribution of PriA, PriB, PriC, and DnaT proteins to cellular DNA replication processes.
Main Methods:
- Biochemical reconstitution of DNA replication with purified proteins.
- Analysis of phenotypes resulting from mutations in genes encoding primosomal proteins (PriA, PriB, PriC, DnaT).
Main Results:
- Primosome assembly, guided by PriA, is essential for specific DNA replication processes like bacteriophage OX174 and ColE1 plasmid replication.
- In vitro replication of oriC plasmids does not necessitate the complete primosome complex.
- Mutational analysis and other data indicate PriA-mediated primosome assembly plays a role in normal cellular DNA replication.
Conclusions:
- PriA-catalyzed primosome assembly is implicated in cellular DNA replication, potentially in reactivating stalled replication forks.
- The study provides evidence supporting the involvement of the primosome in chromosomal DNA replication in E. coli.
Abstract:
The multi-functional PriA protein of Escherichia coli (formerly replication factor Y or protein n') serves to guide the ordered assembly of the primosome, a mobile multiprotein replication priming/helicase complex. Primosome assembly is essential for bacteriophage OX174 complementary DNA strand synthesis and ColE1-type plasmid replication reconstituted in vitro with purified proteins. The biochemical activities of the primosome suggest that it can fulfill the primase/helicase requirement on the lagging-strand DNA template during cellular DNA replication. However, reconstruction in vitro of DNA replication of small plasmids containing the E. coli origin of DNA replication (oriC) does not require the complete complement of primosomal proteins. Thus, the extent to which PriA-catalysed primosome assembly participates in chromosomal replication has remained unclear. The recent isolation of the genes encoding PriA, PriB (protein n), PriC (protein n"), and DnaT (protein i) has provided the necessary tools for addressing this issue. The phenotype of mutations in these genes, and other results described in this review, suggest that assembly of the primosome catalysed by PriA does in fact contribute at some stage to normal cellular DNA replication. A model for primososme-catalysed reactivation of a dysfunctional replication fork is discussed.