Neal A. DeLuca, PhD
514 Bridgeside Point II
450 Technology Drive
PhD in Biophysics, Pennsylvania State University
The pathogenic and cytotoxic effects of viruses are largely due to the expression of viral gene products. Therefore, the determinants of these outcomes are the mechanisms underlying the expression of viral genes. The hallmark of herpes simplex virus gene expression is the sequential and coordinately regulated expression of the approximately 80 viral genes. This regulation occurs largely through modulation of RNA polymerase II transcription. Two viral proteins, VP16 and ICP4, function to activate transcription of the five immediate early genes, and the remainder of the HSV genome, respectively. ICP4 is a large and structurally complex molecule. Previous studies from our lab have provided insight into how this molecule regulates transcription. Considerable effort has been placed on the mechanisms by which the major regulatory protein of HSV, ICP4, affects the pol II transcriptional apparatus of the cell resulting in the regulation of HSV genes. This involves structure/function studies of ICP4 using viral mutants in the context of infection and reconstituted in vitro transcription studies aimed at determining the molecular mechanism of ICP4 function.
In addition, the actions of expressed viral proteins greatly perturbs cellular processes leading to changes in the abundance, activity, and subunit composition of cellular transcription factors. These changes contribute to the pathogenic and cytotoxic effects of HSV and also to the regulated cascade of HSV gene expression. We are using a combination of microarray analysis and protein biochemistry to determine what these changes are as well as their significance to viral gene expression. We have constructed a cDNA chip representing genes for approximately 1500 cellular transcription factors, including components of the basal transcription machinery, coactivator subunits, chromatin remodeling complexes, gene specific regulatory proteins, and viral proteins. The microarray data from infected cells is used to guide the subsequent biochemical experiments.
HSV gene expression during lytic infection is contrasted by the ability to establish latency in PNS neurons. During latency, viral lytic gene expression does not occur, and the genome persists as an episomal element packaged in chromatin. Reactivation from latency presumably involves activation of the genome in the absence of VP16. One IE protein, ICP0, has been shown to be involved in the process of reactivation from latency in several model systems. ICP0 has also been shown to facilitate lytic viral gene expression. While its mechanism of action is unknown, it has been shown to interact with a ubiquitin proteinase and function as a ubiquitin E3 ligase. The use of mutants deficient in subsets of the IE proteins provides the means to examine viral gene expression and genome persistence in the absence of lytic gene expression in tissue culture. One mutant, d109, does not express any of the five IE proteins, is completely nontoxic, and establishes a long-term relationship with the cell. Gene expression from the persisting genomes is repressed, but can be induced by the addition of ICP0. Therefore, some of the events occurring in d109-infected tissue culture cells are similar to those that may occur with latent genomes in vivo. We propose that the activity of ICP0 results in changes to the cellular pathways involved in repression and derepression of gene expression. Two pathways are being investigated, the histone acetylation pathway and the ubiquitin/proteasome pathway. Unlike other latency model systems, the proposed system is very amenable to quantitative biochemical and molecular characterization.
Research Lab Affiliation
Ferenczy, M. W; and DeLuca, N. A. (2011) Reversal of heterochromatic silencing of quiescent herpes simplex virus type 1 by ICP0. J Virol. 85: 3424-3435. | View Abstract
Ferenczy, M. W; and DeLuca, N. A. (2009) Epigenetic modulation of gene expression from quiescent herpes simplex virus genomes. J Virol. 83: 8514-8524. | View Abstract
Hadjipanayis, C. G; Fellows-Mayle, W; and Deluca, N. A. (2008) Therapeutic efficacy of a herpes simplex virus with radiation or temozolomide for intracranial glioblastoma after convection-enhanced delivery. Mol Ther. 16: 1783-1788. | View Abstract
Zabierowski, S. E; and Deluca, N. A. (2008) Stabilized binding of TBP to the TATA box of herpes simplex virus type 1 early (tk) and late (gC) promoters by TFIIA and ICP4. J Virol. 82: 3546-3554. | View Abstract
Sampath, P; and Deluca, N. A. (2008) Binding of ICP4, TATA-binding protein, and RNA polymerase II to herpes simplex virus type 1 immediate-early, early, and late promoters in virus-infected cells. J Virol. 82: 2339-2349. | View Abstract
Terry-Allison, T; Smith, C. A; and DeLuca, N. A.(2007) Relaxed repression of herpes simplex virus type 1 genomes in Murine trigeminal neurons. J Virol. 81: 12394-12405. | View Abstract
Kuddus, R. H; and DeLuca, N. A. (2007) DNA-dependent oligomerization of herpes simplex virus type 1 regulatory protein ICP4. J Virol. 81: 9230-9237. | View Abstract