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Title page for ETD etd-11042010-114906

Type of Document Dissertation
Author Huang, Hao
Author's Email Address hao.huang@vanderbilt.edu
URN etd-11042010-114906
Title Docking of the p68 subunit of DNA polymerase ¦á-primase on the SV40 helicase is required for the viral primosome activity
Degree PhD
Department Biological Sciences
Advisory Committee
Advisor Name Title
James G. Pattion Committee Chair
Brandt F. Eichman Committee Member
Ellen Fanning Committee Member
Katherine L. Friedman Committee Member
Walter J. Chazin Committee Member
  • DNA polymerase alpha-primase
  • DNA helicase
  • p68
  • SV40 primosome
Date of Defense 2010-09-23
Availability unrestricted
DNA polymerase ¦Á-primase (pol-prim) plays a central role in eukaryotic DNA replication, initiating synthesis on both the leading and lagging strand DNA templates. Pol-prim consists of a primase heterodimer that synthesizes RNA primers, a DNA polymerase that extends them, and a fourth subunit, p68, that is thought to regulate the complex. In the Simian Virus 40 (SV40) replication model, the p68 subunit is required for primosome activity and interacts directly with the viral helicase T antigen (Tag), suggesting a functional link between Tag-p68 interaction and primosome activity. To explore this link, I first mapped the interacting regions of the two proteins and discovered a previously unrecognized N-terminal globular domain of p68 (p68N) that physically interacts with the Tag helicase domain. The solution structure of p68N was determined by NMR spectroscopy in the Chazin lab. The putative Tag-interacting surface on p68N was mapped to a hydrophobic patch surrounded by negative charges. Structure-guided mutagenesis of p68 residues in the interface diminished Tag-p68 interaction and primosome activity of the SV40 replisome. The p68N-docking site on Tag was identified using structure-guided mutagenesis of the Tag helicase surface. A charge reversal substitution in Tag specifically disrupted p68N binding, and hence the SV40 primosome activity. These results collectively suggested that the Tag-p68 interaction is vital for SV40 primosome function. A model is presented for how this interaction regulates primosome activity of the pol-prim complex, providing significant insights into the mechanism of eukaryotic DNA replication initiation.
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