Epstein-Barr virus origin of lytic replication mediates association of replicating episomes with promyelocytic leukaemia protein nuclear bodies and replication compartments.

Epstein-Barr virus (EBV) establishes a latent persistence from which it can be reactivated to undergo lytic replication. Late lytic-cycle gene expression is linked to lytic DNA replication, as it is sensitive to the same inhibitors that block lytic replication, and it has recently been shown that the viral origin of lytic replication (ori lyt) is required in cis for late-gene expression. During the lytic cycle, the viral genome forms replication compartments, which are usually adjacent to promyelocytic leukaemia protein (PML) nuclear bodies.

Lytic cycle gene regulation of Epstein-Barr virus.

Episomal reporter plasmids containing the Epstein-Barr virus (EBV) oriP sequence stably transfected into Akata Burkitt's lymphoma cells were used to analyze EBV lytic cycle gene regulation. First, we found that the Zp promoter of EBV, but not the Rp promoter, can be activated in the absence of protein synthesis in these oriP plasmids, casting doubt on the immediate early status of Rp. An additional level of regulation of Zp was implied by analysis of a mutation of the ZV element.

Reactivation of Epstein-Barr virus from latency.

The general problem in cancer treatment centres on finding agents that specifically affect cancer cells without damaging normal cells. The differences between cancer cells and normal cells are usually very subtle but about 15% of all human cancers involve a virus infection, for example the Epstein-Barr virus associated cancers. In these cancers, every tumour cell carries the virus in a latent infection but the number of normal cells infected is very low.

Promoter sequences required for reactivation of Epstein-Barr virus from latency.

A luciferase reporter system with stably transfected oriP plasmids in Akata Burkitt's lymphoma cells provides a quantitative assay for the BZLF1 Zp promoter in response to B-cell receptor (BCR) activation by cross-linking with anti-immunoglobulin. In this system, detailed kinetic studies of promoter activity are possible. Previously reported promoter elements upstream of -221 from the transcription start and the ZIIR sequence had little effect on the Zp promoter, but the ZI and ZIIIA elements were essential for early activation.