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Department of Biomedical Sciences > Research > Faculty Research & Labs

Kaplan Lab

Daniel Kaplan

Florida State University
College of Medicine
1115 West Call Street
Tallahassee, FL 32306-4300
Office: (850) 645-1481, MSR 3350-C
Lab: (850) 645-2929, MSR 3310-L

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Dr. Kaplans's Faculty Profile
Spotlight on Science: Kaplan Lab

Research Interests

 The Kaplan Lab—DNA Replication and Genome Maintenance

DNA replication is a key process in living cells that is important for cell growth and division.  Disruption of DNA replication in higher organisms may lead to genome instability, which may ultimately result in a disease state such as cancer.  Our lab is principally interested in how cells replicate their genomic DNA in eukaryotic cells in order to maintain faithful inheritance of the genome.

              DNA replication is initiated by chromosomal unwinding, a process wherein the replication fork helicase separates the duplex genomic DNA into single strands.  The single stranded DNA can then serve as a template for DNA polymerases to carry out faithful replication of the genome. The replication fork helicase in eukaryotes is composed of the Mcm2-7 heterohexamer, Cdc45, and the tetrameric GINS complex.  The Mcm proteins serve as useful makers for cancer, and understanding how these proteins function may lead to further advancement in the development of cancer prognostic and diagnostic tools.  Understanding how the replication fork helicase initiates unwinding in eukaryotic cells to initiate DNA replication is a focus of study in our laboratory.  We are also interested in determining how unwinding at a replication fork is coupled with DNA duplication, and the cellular polymerases pol alpha, pol delta, and pol epsilon catalyze synthesis of DNA.

DNA Replication

 

Current Research Projects

 

 

               The initiation of DNA replication in eukaryotes is regulated by cellular kinases, including the Dbf4-Cdc7 kinase, and the S-phase cyclin-dependent kinase.  These kinases act upon components of the replication fork to activate the replication fork helicase.  These kinases are currently the targets for chemotherapeutic agents because of their central role in controlling the initiation of DNA replication.  Three proteins required for DNA replication initiation in budding yeast cells, Sld2, Sld3, and Dpb11, do not travel with the replication fork.  We are investigating the mechanism of action of Sld2, Sld3, and Dpb11 because they are central to understanding how DNA replication is initiated.  We are also investigating the mechanism of Mcm10, an additional essential replication initiation factor.  Finally, we are investigating how DNA replication is coordinated with histones and histone chaperones.

               Our investigations will yield essential information about how DNA replication is initiated and regulated in eukaryotic cells.  Importantly, we will provide a detailed, mechanistic, and dynamic understanding of how the protein machines that initiate replication function in a cell.  The advances that we make will likely lead to improvements in the treatment of cancer.  Some of the proteins that we study are also involved in the DNA damage response.  Thus, an additional emphasis is to determine how the DNA damage response functions to allow cells to survive upon challenge by agents that are toxic to DNA.

 

Current Laboratory Members

Daniel KaplanDaniel L. Kaplan Irina Bruck

Patricia Perez

Max Colbert

 

 

Maurice Facey

 

 

Matt Jones

 

 

 

 

 

 

 

 

 

 

Selected References

  1. C Eielson, D Kaplan, MA Mitnick, I Paliwal, K Insogna. “Estrogen modulates parathyroid hormone-induced fibronectin production in human and rat osteoblast-like cells.” Endocrinology 135: 1639-1644 (1994). PMID: 8647916. 
  2. DL Kaplan, WF Boron. “Long-term expression of c-H-ras stimulates Na-H and Na+-dependent Cl-HCO3 exchange in NIH 3T3 fibroblasts.” J. Biol. Chem. 269: 4116-4124 (1994). PMID: 8307971.
  3. DL Kaplan, CM Eielson, MC Horowitz, KL Insogna, EC Weir. “Tumor necrosis factor-alpha induces transcription of the colony-stimulating factor 1 gene in murine osteoblasts.” J. Cell Physiol. 168: 199-208 (1996). PMID: 8647916. 
  4. DL Kaplan, TA Steitz. “DnaB from Thermus aquaticus Unwinds Forked Duplex DNA with an Asymmetric Tail Length Dependence.” J. Biol. Chem. 274: 6889-6897 (1999). PMID: 10066742
  5. DL Kaplan. “The 3’-tail of a Forked-Duplex Sterically Determines Whether One or Two DNA Strands Pass Through the Central Channel of a Replication Fork Helicase.” J. Mol. Biol. 301: 285-299 (2000). PMID: 10926510.
  6. DL Kaplan, M O'Donnell. “DnaB Drives DNA Branch Migration and Dislodges Proteins While Encircling Two DNA Strands.” Mol. Cell 10: 647-657 (2002). PMID: 12408831. 
  7. DL Kaplan and M O’Donnell. “Rho Factor: Transcription Termination in Four Steps.” Curr. Biol. 13: R714-R716 (2003). PMID: 13678611. 
  8. DL Kaplan, MJ Davey, M O'Donnell. “Mcm4,6,7 Uses ‘Pump in Ring’ Mechanism to Unwind DNA by Steric Exclusion and Actively Translocate Along a Duplex.” J. Biol. Chem. 278: 49171-49182 (2003). PMID: 13679365. 
  9. DL Kaplan and M O'Donnell. “Twin DNA Pumps of a Hexameric Helicase Provide Power to Simultaneously Melt Two Duplexes.” Mol. Cell 15: 453-465 (2004). PMID: 15304224. 
  10. DL Kaplan and M O'Donnell. “RuvA Is a Sliding Collar that Protects Holliday Junctions from Unwinding while Promoting Branch Migration.” J. Mol. Biol. 355: 473-490 (2006). PMID: 16324713. 
  11. DL Kaplan. “Replication Termination: Mechanism of Polar Arrest Revealed.” Curr. Biol. 16: R684-686 (2006). PMID: 16950091. 
  12. DM Kanter, I Bruck, and DL Kaplan. “Mcm subunits can assemble into two different active unwinding complexes.” J. Biol. Chem. 283:31172-1182 (2008). PMID: 18801730. 
  13. DL Kaplan and D Bastia. “Mechanisms of polar arrest of a replication fork.” Mol. Microbiol. 72:27-285 (2009). PMID: 19298368. 
  14. I Bruck and D Kaplan. “Dbf4-Cdc7 phosphorylation of Mcm2 is required for cell growth.” J. Biol. Chem. 284:28823-31 (2009). PMID: 19692334. 
  15. DL Kaplan and I Bruck. “Methods to study kinase regulation of the replication fork helicase.” Methods. 51:358-62 (2010). PMID: 20170732. 
  16. CE Wickersham, KJ Cash, SH Pfeil, I Bruck, DL Kaplan, KW Plaxco, and EA Lipman. “Tracking a molecular motor with a nanoscale optical encoder.” Nano Lett. 10:1022-1027 (2010). PMID: 20121107. 
  17. DL Kaplan and I Bruck. “Methods to study how replication fork helicases unwind DNA.” Methods Mol Biol. 587:127-35 (2010). PMID: 20225146
  18. N Ribeck, DL Kaplan, I Bruck, OA Saleh, “DnaB helicase activity is modulated by DNA geometry and force.” Biophys J. 99:2170-9 (2010). PMID: 20923651
  19. DM Kanter and DL Kaplan, "Sld2 binds to origin ssDNA and stimulates DNA annealing." Nucleic Acids Res. 39: 2580-2592 (2011) PMID: 21109535. 
  20. I. Bruck and DL Kaplan, "GINS and Sld3 compete with one another for Mcm2-7 and Cdc45 binding." J. Biol. Chem. 286:14157-67 (2011) PMID: 21362622. 
  21. I. Bruck and DL Kaplan, "Origin Single-stranded DNA Releases Sld3 Protein from the Mcm2-7 Complex, Allowing the GINS Tetramer to Bind the Mcm2-7 Complex." J. Biol. Chem. 286:18602-13 (2011) PMID: 21460226. 
  22. I. Bruck, DM Kanter, and DL Kaplan "Enabling Association of the GINS Protein Tetramer with the Mini Chromosome Maintenance (Mcm)2-7 Protein Complex by Phosphorylated Sld2 Protein and Single-stranded Origin DNA." J. Biol. Chem. 286:36414-26 (2011) PMID: 21868389. 
  23. AN Suhasini, JA Sommers, S Yu, Y Wu, T Zu, Z Kelman, DL Kaplan, and RM Brosh, Jr. "DNA Repair and Replication Fork Helicases are Diffferentially Affected by an Alkyl Phosphotriester Lesion." J. Biol. Chem. 287:19188-98 (2012) PMID: 22465574.
  24. DL Kaplan, OA Saleh, and N Ribeck. “Single-molecule and bulk approaches to the DnaB replication fork helicase.”  Front Biosci. 18: 224-40 (2013) PMID: 23276919.
  25. I Bruck and DL Kaplan "Cdc45-ssDNA interaction is important for stalling the helicase during replication stress." J Biol Chem. 288:7550-63 (2013) PMID: 23382391. 
  26. I Bruck and DL Kaplan "The Replication Initiation Protein Sld2 Regulates Helicase Assembly."  J Biol Chem.  289: 1948-59 (2014) PMID: 24307213.
  27. Bharti SK, Sommers JA, Zhou J, Kaplan DL, Spelbrink JN, Mergny JL, Brosh RM Jr. "DNA Sequences Proximal to Human Mitochondrial DNA Deletion Breakpoints Prevalent in Human Disease Form G-quadruplexes, a Class of DNA Structures Inefficiently Unwound by the Mitochondrial Replicative Twinkle Helicase." J. Biol. Chem. 289:29975-93 (2014) PMID:  25193669. 
  28. Khan I, Suhasini AN, Banerjee T, Sommers JA, Kaplan DL, Kuper J, Kisker C, Brosh RM Jr. "Impact of age-associated cyclopurine lesions on DNA repair helicases."PLoS One. 9:e113293 (2014) PMID: 25409515.
  29. I Bruck and DL Kaplan "The Dbf4-Cdc7 kinase promotes Mcm2-7 ring opening to allow for single-stranded DNA extrusion and helicase assembly. J. Biol. Chem. 290:1210-21 (2015) PMID: 25471369
  30. Dhingra N, Bruck I, Smith S, Ning B, Kaplan DL. "Dpb11 protein helps control assembly of the Cdc45·Mcm2-7·GINS replication fork helicase." J Biol Chem. 290(12):7586-601. (2015) PMID: 25659432.
  31. Bruck I, Kaplan DL. "Conserved mechanism for coordinating replication fork helicase assembly with phosphorylation of the helicase." Proc Natl Acad Sci U S A. 112:11223-8. (2015) PMID: 26305950.
  32. Bruck I, Kaplan DL. "The Replication Initiation Protein Sld3/Treslin Orchestrates the Assembly of the Replication Fork Helicase during S Phase." J Biol Chem. 290:27414-24. (2015) PMID: 26405041.
  33. Bruck I, Perez-Arnaiz P, Colbert MK, Kaplan DL. "Insights into the Initiation of Eukaryotic DNA Replication." Nucleus. Dec 28:1-6. [Epub ahead of print] (2015) PMID: 26710261.
  34. Perez-Arnaiz P, Bruck I, Kaplan DL. "Mcm10 coordinates the timely assembly and activation of the replication fork helicase." Nucleic Acids Res. 44:315-29 (2016) PMID: 26582917.