Initiation of DNA replication is a complicated process that is understood in only very broad terms. At present, the best eukaryotic model for studies of initiation of DNA replication is the Simian Virus 40 (SV4O) in vitro replication system. Initiation of SV4O replication requires a single viral protein termed T-antigen (T-ag). Critical roles played by T.ag during initiation of replication include site specific binding to the SV4O origin, catalysis of subsequent unwinding events and recruitment of additional proteins necessary for initiation of DNA synthesis. However, our understanding of these events is limited owing to a lack of structural information about T-ag or the T-ag DNA binding domain (T-ag-bd). The following specific aims are proposed to address these issues. I. To determine the structure of the DNA binding domain of SV4O T-antigen. II. To characterize the biochemical properties of the T-ag-bd, and of certain mutant forms of the T-ag-bd, and to examine the structures of those mutant forms of the T-ag-bd with interesting properties. III. To delineate the interaction of the T-ag-bd with DNA. The work proposed in this application is significant from a basic science standpoint because it will provide the first structure of a protein domain that recognizes an origin of replication, whether from a prokaryotic or eukaryotic source. Moreover, existing sequence data indicate the T-ag-bd is not related to other known DNA binding proteins, suggesting the structure may reveal a new protein structural motif. A knowledge of this structure, or of the structure of this domain complexed to DNA, will contribute significantly to advancing our understanding of replication by revealing the protein/DNA contacts that enable specific recognition and binding to an origin of replication. The health related significance of the work proposed stems from the fact that SV4O T-ag is very homologous to the T-ags encoded by the BK and JC viruses. These viruses induce a number of diseases in humans, including cancer. For example, JC virus induces progressive multifocal leukoencephalopathy, a disease present in many AIDS patients.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM053618-04
Application #
2872703
Study Section
Experimental Virology Study Section (EVR)
Project Start
1996-02-01
Project End
2000-01-31
Budget Start
1999-02-01
Budget End
2000-01-31
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Tufts University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02111
Bradshaw, Elizabeth M; Sanford, David G; Luo, Xuelian et al. (2004) T antigen origin-binding domain of simian virus 40: determinants of specific DNA binding. Biochemistry 43:6928-36
Kim, H Y; Barbaro, B A; Joo, W S et al. (1999) Sequence requirements for the assembly of simian virus 40 T antigen and the T-antigen origin binding domain on the viral core origin of replication. J Virol 73:7543-55
Bullock, P A (1997) The initiation of simian virus 40 DNA replication in vitro. Crit Rev Biochem Mol Biol 32:503-68