Methylation of CpG motifs has been identified as a global mechanism in the silencing of genes and it has been hypothesized that methylation is a critical component in the silencing of lytic viral genes during the establishment of latency of gammaherpesviruses. Human gammaherpesviruses such as Epstein Barr virus and Campos's Sarcoma Herpes virus are associated with several lymphoproliferative disorders. In vitro research has shown that during latency the promoter regions of genes necessary for lytic viral replication are hypermethylated while the promoters of latency-associated genes are hypomethylated. Since in vivo studies of these viruses are difficult due to their limited host range, gammaherpesvirus 68 (gHV68) is used as a model to study the effects of gammaherpesviruses in vivo. To address the role of cellular methyltransferases and methylation in the establishment and maintenance of latency of the virus, we propose to investigate the amount of methylation of both lytic and latent promoters during different time points of infection in the mouse. The level of methylation will be compared to the amount of lytic- and latency-specific viral transcripts present at the different days postinfection. Finally, the effect of the deletion of the cellular methyltransferase, Dnmt1, in gHV68-infected cells on the establishment of latency will be analyzed using the cre-lox gene-targeting system. These studies will advance our understanding of the mechanisms that govern the establishment and maintenance of latency in vivo.
