AN EBNA-1-DEPENDENT ENHANCER ACTS FROM A DISTANCE OF 10-KILOBASE PAIRS TO INCREASE EXPRESSION OF THE EPSTEIN-BARR-VIRUS LMP GENE

Upon infection of human B lymphocytes, the 172-kbp Epstein-Barr virus genome forms a covalently closed circle via its terminal repeats. This event brings all of the promoters that control expression of the latent gene products, and the viral origin of plasmid replication, oriP, within a 20-kbp stretch of contiguous DNA. We have found that the EBNA-1-dependent transcriptional enhancer FR, located in oriP, increased the expression of a tagged viral oncogene encoding the latent membrane protein (LMP) up to 200-fold in normal Epstein-Barr virus-positive cells. The effect of FR was exerted across 10 kbp of viral DNA that spans the circularized ends of the viral genome. Enhancement of the tagged LMP gene by FR/EBNA-1 did not require the EBNA-2-responsive element.