Molecular basis of pathogenesis of the herpesviruses, and application of these pathogenic concepts to the development of HSV as a gene therapy vector
1) Determining the molecular basis of HSV latency and reactivation. A major focus of my laboratory during the past 5 years has involved mapping the genetic elements in the HSV-1 genome that respond to stress and facilitate reactivation from latency. To this end we have demonstrated that a ~650 bp region (reactivation critical region or rcr) within the Latency-Associated Transcript (LAT) locus is required for efficient reactivation. We have demonstrated that this region does not function in trans. Our recent work has shown that this region is enriched in acetylated histones during latency. Our current model is that association of the acetyl histones with the rcr is linked to its activity as a transcriptional enhancer. It is our hypothesis that this enhancer is part of a key regulatory element that may alter the transcriptional permissivity of this region of the HSV genome to regulate lytic vs. latent functions.
2) Identifying molecular determinants of HSV latent gene expression and silencing of lytic genes. This second major focus of my lab centers around defining the transcriptional mechanisms responsible for silencing lytic genes during latency, but still allowing the LAT to be abundantly transcribed. Our long-standing hypothesis has been that an epigenetic mechanism is likely involved in transcriptional silencing during HSV-1 latency. To this end we have determined that while DNA methylation does not seen to regulate genes during latency, the association of modified histones with the latent HSV-1 episomes does correlate with transcriptional repression and activation. This work suggests the HSV-1 genome is organized into functional transcriptional domains that are organized at the level of chromatin, similar to the organization of cellular chromosomes. Work is currently focused on mapping boundary or insulator elements that separate regions of transcriptionally repressed chromatin from transcriptionally active ones, and identifying the specific cis and trans factors that direct the establishment (and regulation) of these structures.
3) Exploiting HSV's unique biology and developing improved versions of HSV vectors for expressing biologically relevant peptides in neurons of the peripheral and central nervous systems. A final area of focus of my lab is aimed at developing HSV as a vector for gene therapy. We have modified existing HSV-1 vectors to enhance their expression properties in the nervous system. As applications we have aimed to: 1) deliver HSV vectors to the eye (to reach the trigeminal ganglia) as a potential therapy for recurrent stromal keratitis; 2) deliver biological peptides to the CNS (as a potential therapy for Fragile X Disease), and 3) develop safer oncolytic viruses for anti-glioma therapies.
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