Using a tumor virus, we are defining the events that occur during the initiation of DNA replication. Initiation of DNA replication is a complicated process that is known to take place in many stages;these include the recognition of the viral origin by the virally encoded initiator protein, subsequent oligomerization events that are coupled to structural distortions of the origin, transition of the initiator into a 3'->5'helicase and recruitment of cellular factors for subsequent steps in initiation. Recent advances in the determination the structure of T-ag have contributed much to our understanding of its role in catalyzing the initiation of DNA replication. We have focused our structural studies on the domain of T-ag that site specifically recognized the origin. Using x-ray crystallography, we determined that this domain forms a 'spiral-hexamer'and solved the co-structure of the T-ag-obd bound to an origin sub-fragment containing two pentanucleotides. These structures have significantly increased our understanding of the architectural arrangement of viral origins, the precise mechanism of origin recognition and provided critical insights into origin specific unwinding. However, additional structural information is now needed in order to understand the initiation process. Additional experiments led to the identification of the 'beta-hairpin1;a motif that is present in the initiators encoded by a broad spectrum of DNA tumor viruses. Preliminary studies indicated that this motif is needed for origin recognition, melting of duplex DNA and subsequent helicase activities. Therefore, we will establish the exact role(s) played by the """"""""beta-hairpin"""""""" during initiation of viral replication. For example, we will extend recent studies indicating that the tip of the """"""""beta-hairpin"""""""" plays an active role in melting origin DNA and that the ssDNA generated in this process is needed for subsequent assembly events. BRCT domains are known to recruit proteins involved in cell-cycle control, DNA repair and recombination. Our recent analyses indicate that a BRCT family member is present in the helicase domain of T-ag. Using techniques and approaches developed by individuals in the BRCT field, we will confirm that a BRCT motif is present in T-ag. This observation has the potential to greatly advance our understanding of how SV40 causes the myriad changes in the cells that it infects. Relevance to Public Health: Recent studies have demonstrated that the initiation of DNA replication in DNA tumor viruses is highly conserved. Therefore, a thorough description of initiation in one or two model systems will have broad ramifications in terms of our understanding of the propagation of diverse pathogens. These studies will also serve as a paradigm when considering how DNA replication is initiated in higher-eukaryotic organisms.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM055397-16S1
Application #
7921883
Study Section
Virology - A Study Section (VIRA)
Program Officer
Santangelo, George M
Project Start
2009-09-30
Project End
2011-03-31
Budget Start
2009-09-30
Budget End
2011-03-31
Support Year
16
Fiscal Year
2009
Total Cost
$271,117
Indirect Cost
Name
Tufts University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
039318308
City
Boston
State
MA
Country
United States
Zip Code
02111
Meinke, Gretchen; Phelan, Paul J; Harrison, Celia J et al. (2013) Analysis of the costructure of the simian virus 40 T-antigen origin binding domain with site I reveals a correlation between GAGGC spacing and spiral assembly. J Virol 87:2923-34
Harrison, Celia J; Meinke, Gretchen; Kwun, Hyun Jin et al. (2011) Asymmetric assembly of Merkel cell polyomavirus large T-antigen origin binding domains at the viral origin. J Mol Biol 409:529-42
Meinke, Gretchen; Phelan, Paul J; Fradet-Turcotte, Amélie et al. (2011) Structure-based analysis of the interaction between the simian virus 40 T-antigen origin binding domain and single-stranded DNA. J Virol 85:818-27
Meinke, Gretchen; Phelan, Paul; Fradet-Turcotte, Amélie et al. (2011) Structure-based design of a disulfide-linked oligomeric form of the simian virus 40 (SV40) large T antigen DNA-binding domain. Acta Crystallogr D Biol Crystallogr 67:560-7
Fradet-Turcotte, Amelie; Morin, Genevieve; Lehoux, Michael et al. (2010) Development of quantitative and high-throughput assays of polyomavirus and papillomavirus DNA replication. Virology 399:65-76
Kumar, Anuradha; Joo, Woo S; Meinke, Gretchen et al. (2008) Evidence for a structural relationship between BRCT domains and the helicase domains of the replication initiators encoded by the Polyomaviridae and Papillomaviridae families of DNA tumor viruses. J Virol 82:8849-62
Meinke, Gretchen; Phelan, Paul; Moine, Stephanie et al. (2007) The crystal structure of the SV40 T-antigen origin binding domain in complex with DNA. PLoS Biol 5:e23
Kumar, Anuradha; Meinke, Gretchen; Reese, Danielle K et al. (2007) Model for T-antigen-dependent melting of the simian virus 40 core origin based on studies of the interaction of the beta-hairpin with DNA. J Virol 81:4808-18
Fradet-Turcotte, Amelie; Vincent, Caroline; Joubert, Simon et al. (2007) Quantitative analysis of the binding of simian virus 40 large T antigen to DNA. J Virol 81:9162-74
Reese, Danielle K; Meinke, Gretchen; Kumar, Anuradha et al. (2006) Analyses of the interaction between the origin binding domain from simian virus 40 T antigen and single-stranded DNA provide insights into DNA unwinding and initiation of DNA replication. J Virol 80:12248-59

Showing the most recent 10 out of 21 publications