Staff Biography
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RONA S. SCOTT, PhDResearch Assistant Professor
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Contact Phone: (318) 675-6263 Team Membership |
Education /Research / Publications
Education / Professional Experience
Postdoctoral Study, University of North Carolina at Chapel Hill and Louisiana State University Health Sciences Center-Shreveport
Ph.D., Biochemistry, 1997, University of North Carolina at Chapel Hill
Research Interest
Mechanisms for Epstein-Barr virus-mediated tumor progression
The long-term goal of our laboratory is to delineate mechanisms by Epstein-Barr virus (EBV) mediates tumor progression. Two major areas are currently being investigated. The first research area involves understanding how the terminal repeats of EBV influence the expression of latent membrane proteins 1 and 2A, known EBV oncoproteins. The second area involves determining epigenetic changes induced upon EBV infection that can contribute to tumorigenesis, and whether the epigenetic changes are retained upon loss of the virus.
Epstein-Barr virus (EBV) is a human DNA virus that persistently infects over 90% of the adult population, usually without consequence. However, EBV is linked to a diverse assortment of lymphoid and epithelial malignancies originating at various anatomical sites. Thus, the main goal of our laboratory is delineate the mechanisms by which EBV mediates tumor progression. Upon infection, EBV circularizes by homologous recombination via its terminal repeats (TR). Each circularization events generates a unique fragment with a variable number of TRs. Clonality of the EBV TRs in tumors has been used as a determinant for assigning a role for EBV in the initiation of tumorigenesis. However, we hypothesize that clonal EBV TRs can arise through the selection of viral episomes that have optimal expression of viral oncoproteins, latent membrane proteins (LMP) 1 and 2A (Project 1). Intron 1 of LMP2A is comprised of the fused TR fragment and the epithelial promoter of LMP1 is located within the first TR. Indeed, we have shown that TR number inversely correlates with LMP2A and LMP1 expression. Understanding the molecular mechanisms of TR regulation of LMP1 and 2A will provide a basis for TR clonal selection during tumorigenesis and solidify the role of EBV in tumor progression.
A second focus (Project 2) of the lab involves understanding the partial association of EBV in tumors of similar histogenetic phenotype. The association with any one tumor is often erratic, with only a percentage carrying the virus. Thus, only 10% of gastric carcinomas bear virus compared to virtually all undifferentiated nasopharyngeal carcinomas. More recent findings indicate that not all tumor cells within established EBV-associated malignancies retain EBV. Thus, our laboratory is interested in understanding the mechanisms of EBV-driven tumorigenesis in the context of incomplete viral association in cancer.
Specific Interests:
Epstein-Barr Virus
Epigenetics
DNA Methylation and chromatin Structure
MicroRNA
Defective viruses
Project 1/ Carcinomas: Understanding the role of the terminal repeat number (TR) of Epstein-Barr virus in tumorigenesis. Upon infection, EBV circularizes by homologous recombination of its TR to generate a fused fragment with variable number of repeats. LMP2A and LMP1 are two important oncoproteins of EBV whose expression can be governed by the TR. Intron 1 of the LMP2A transcript is contains the TR, and increasing size of TR can reduce its expression. In epithelial cells, the LMP1 promoter is within the first TR of EBV, thus variations in TR can influence the expression of these two proteins. Thus, we are investigating the mechanisms that regulate expression of these two gene products including methylation and differential splicing. We have also created a GFP reporter system to investigate the effects of in vitro manipulation of TR number on GFP expression.
Project 2/ Carcinomas with emphasis on breast carcinoma: Preliminary data from our laboratory now suggest that transient infection of carcinoma cell lines by EBV in vitro can stably alter cell morphology and gene expression patterns, such that the resultant phenotype is retained by cell progeny for generations after EBV DNA loss. Reversion to the parental phenotype on treatment with 5-aza-2-deoxycytine, an inhibitor of methyltransferases, suggests an epigenetic effect. LMP1 has been shown to induce the DNA methyltransferases resulting in methylation and silencing of the e-cadherin promoter. In addition, EBV encodes a number of microRNAs that may be able to target methylation in a sequence specific manner as has been shown for siRNAs. We propose a model whereby EBV infection of tumor tissue alters the infected cell epigenetically, such that EBV’s continued presence would no longer be required to provide a selective advantage to the tumor cell. In addition, we are also investigating whether defective EBV viruses accelerate loss of EBV DNA and contribute to the partial association of EBV in certain cancers.
Laboratory experise:
1. Cell culture including viral infection and virus production (EBV and retrovirus)
2. Transfection, generation of stable lines.
3. Recombinant DNA techniques/ cloning
4. Bacterial artificial chromosomes
5. Pulse field gel electrophoresis, Southern blotting
6. Northern blotting
7. Real-time quantitative PCR
8. Affymetrix microarray expression profiling
9. DNA methylation analysis: Bisulfite modification and sequencing/ methylation sensitive PCR
10. Protein Immunoprecipitation and Western blotting
11. ChIP on Chip
12. Bioinformatics
Selected Publications
Scott, R. S., K. Y. Truong, and J.-M. H. Vos. 1997. Replication initiation and elongation forks rates within a differentially expressed human multicopy locus in early S phase. Nucleic Acids Res. 25: 4505-4512.
Scott, R. S., E. J. McMahon, S.M. Pop, E. A. Reap, R. Caricchio, P. L. Cohen, H. S. Earp, and G. K. Matsushima. 2001. Phagocytosis and clearance of apoptotic cells is mediated by Mer. Nature. 411: 207-211.
Moody C. A., R. S. Scott, T. Su, J.W. Sixbey, 2003. Length of Epstein-Barr Virus Termini as a Determinant of Epithelial Cell Clonal Emergence. J. Virol. 77: 8555-61.
Wagner, H-J. R. S. Scott, D. Buchwald, and J.W. Sixbey. 2004. Peripheral blood lymphocytes express recombinase activating genes (RAG) 1 and 2 during Epstein-Barr virus (EBV)-induced infectious mononucleosis. J. Infect Dis. 190(5):979-84.
Scott, R. S., C. A. Moody, and J. Sixbey. 2005. Epstein-Barr virus and oral malignancies. In: Robertson E (ed). Epstein-Barr virus: Pathogenesis, Molecular Biology, and Infection. Horizon Scientific Press/Caister Academic Press, Norfolk, U.K.
Moody, C. A, R. S. Scott, N. Amirghahari, C-A. Nathan, L. S. Young, C. W. Dawson, J. W. Sixbey. 2005. Modulation of the cell growth regulator mTOR by Epstein-Barr virus-encoded LMP2A. J Virol.: 79(9):5499-5506.