Previous Article | Next Article ![]()
J. Virol., Sep 1997, 6445-6454, Vol 71, No. 9
KD Robertson and RF Ambinder
Methylation-associated transcriptional repression is recognized in many
settings and may play a role in normal differentiation and in
tumorigenesis. Both sequence-specific and nonspecific mechanisms have been
elaborated. Recently, we have presented evidence that methylation-
associated inhibition of the Epstein-Barr virus (EBV) major latency
promoter (BamHI C promoter or Cp) in Burkitt's lymphoma and Hodgkin's
disease may play an important role in the pathogenesis of these tumors by
protecting them from CD8+ cytotoxic T-cell immunosurveillance. The
mechanism of transcriptional repression may relate to specific inhibition
of the binding of a cellular transcription factor by methylation. To
dissect the viral promoter with regard to transcriptional sensitivity to
methylation, we have devised an assay that allows the methylation of
discrete regions of reporter plasmids. During the course of the assay,
methylation patterns appeared to be stable; there was no evidence of either
spread or reversal of the imposed methylation pattern. Application of the
assay to the 3.8-kb region upstream of the major EBV latency promoter with
natural Cp reporter plasmids showed that sensitivity to methylation is not
homogeneously distributed but is concentrated in two discrete regions. The
first of these methylation-hypersensitive regions (MHRI) is the previously
identified EBNA-2 response element, which includes the
methylation-sensitive CBF2 binding site. The second (MHRII) is a sequence
further downstream whose potential role in methylation- mediated
transcriptional repression had been previously unsuspected. In chimeric
enhancer/promoter plasmids, methylation of this downstream region was
sufficient to virtually abolish simian virus 40 enhancer- driven
transcription. Further dissection indicated that methylation of the EBNA-2
response element (MHRI) was sufficient to abolish EBNA-2- mediated Cp
activity while methylation of a region including the EBNA-2 response
element and downstream sequence (MHRI and MHRII) was sufficient to abolish
all Cp-mediated reporter activity, including that driven by the
EBNA-1-dependent enhancer in the origin of plasmid replication, oriP.
Copyright © 1997, American Society for Microbiology
Mapping promoter regions that are hypersensitive to methylation- mediated inhibition of transcription: application of the methylation cassette assay to the Epstein-Barr virus major latency promoter
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
This article has been cited by other articles:
| J. Bacteriol. | Mol. Cell. Biol. | Microbiol. Mol. Biol. Rev. |
|---|
| Clin. Vaccine Immunol. | ALL ASM JOURNALS |
|---|