All cellular organisms rely on a multi-protein molecular machine named the replisome to duplicate their genomes. At replication origins, assembly of replisomes for chromosomal DNA replication is a highly regulated event that is coordinated with the cell cycle. In Escherichia coli, DnaA protein initiates chromosomal DNA replication by orchestrating a step-wise process that leads to two DNA helicases bound to each parental DNA strand, which is necessary for bidirectional fork movement from the chromosomal origin. Other components of the replisome then assemble at the newly formed replication fork. Duplication of the genome follows. The recruitment of the replicative helicase to the chromosomal origin is a critical step during the initiation stage of DNA replication. The long-term objective of this research is to understand the molecular mechanism of recruitment and activation of DnaB, the replicative helicase of Escherichia coli, via genetic, biochemical and molecular biological methods. Because all free-living organisms use a similar mechanism of initiation, these studies should provide insight into how this event occurs in higher organisms.

Public Health Relevance

Chromosomal DNA replication is an essential process that occurs by similar biochemical mechanisms in all free-living organisms. At the replication origin of the Escherichia coli chromosome, a critical event is the loading and activation of the DNA helicase that functions to unwind the duplex DNA to propagate movement of the replication fork. This project investigates the molecular mechanism of recruitment and activation of DnaB helicase during the initiation of chromosomal replication;these studies may lead to novel methods to treat human diseases caused by bacterial pathogens.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Reddy, Michael K
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Michigan State University
Schools of Arts and Sciences
East Lansing
United States
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Kim, Jin S; Nanfara, Michael T; Chodavarapu, Sundari et al. (2017) Dynamic assembly of Hda and the sliding clamp in the regulation of replication licensing. Nucleic Acids Res 45:3888-3905
Felczak, Magdalena M; Chodavarapu, Sundari; Kaguni, Jon M (2017) DnaC, the indispensable companion of DnaB helicase, controls the accessibility of DnaB helicase by primase. J Biol Chem 292:20871-20882
Felczak, Magdalena M; Sage, Jay M; Hupert-Kocurek, Katarzyna et al. (2016) Substitutions of Conserved Residues in the C-terminal Region of DnaC Cause Thermolability in Helicase Loading. J Biol Chem 291:4803-12
Chodavarapu, Sundari; Jones, A Daniel; Feig, Michael et al. (2016) DnaC traps DnaB as an open ring and remodels the domain that binds primase. Nucleic Acids Res 44:210-20
Chodavarapu, S; Kaguni, J M (2016) Replication Initiation in Bacteria. Enzymes 39:1-30
Bell, Stephen P; Kaguni, Jon M (2013) Helicase loading at chromosomal origins of replication. Cold Spring Harb Perspect Biol 5:
Chodavarapu, Sundari; Felczak, Magdalena M; Simmons, Lyle A et al. (2013) Mutant DnaAs of Escherichia coli that are refractory to negative control. Nucleic Acids Res 41:10254-67
Felczak, Magdalena M; Kaguni, Jon M (2012) The rcbA gene product reduces spontaneous and induced chromosome breaks in Escherichia coli. J Bacteriol 194:2152-64
Kaguni, Jon M (2011) Replication initiation at the Escherichia coli chromosomal origin. Curr Opin Chem Biol 15:606-13
Chodavarapu, Sundari; Felczak, Magdalena M; Kaguni, Jon M (2011) Two forms of ribosomal protein L2 of Escherichia coli that inhibit DnaA in DNA replication. Nucleic Acids Res 39:4180-91