Repression of Epstein-Barr virus EBNA-1 gene transcription by pRb during restricted latency.
Repression of Epstein-Barr virus EBNA-1 gene transcription by pRb during restricted latency.
复制标题
pRb 在限制潜伏期抑制 Epstein-Barr 病毒 EBNA-1 基因转录。
DOI：
10.1128/jvi.73.10.7943-7951.1999
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发表时间：
1999
影响因子：
5.4
通讯作者：
Sample,J
中科院分区：
文献类型：
--
作者：
Ruf,IK;Sample,J
During the restricted programs of Epstein-Barr virus (EBV) latency in EBV-associated tumors and a subpopulation of latently infected B cells in healthy EBV carriers, transcription of the EBV nuclear antigen 1 (EBNA-1) gene is mediated by the promoter Qp. Previously, two noncanonical E2F binding sites were identified within Qp. The role of E2F in the regulation of Qp, however, has been controversial and is undefined. Here we demonstrate that an E2F factor(s) within Burkitt lymphoma (BL) cells binds to a G/C-rich element [GGCG(C/G)] within the previously identified binding sites in Qp and prototypical E2F response elements. Furthermore, Qp-driven reporter gene expression could be efficiently repressed through either E2F binding site by the tumor suppressor pRb, a potent transcriptional repressor targeted to promoters during G0and the early G1phase of the cell cycle via its interaction with E2F; a mutant pRb (pRb706) lacking E2F binding capability was unable to repress Qp. However, we did not observe cell cycle variation in the expression of either EBNA-1 mRNA or protein in exponentially growing BL cells, consistent with previous predictions that Qp is constitutively active in these cells and with the extremely longt1/2of EBNA-1. By contrast, within G0/G1in growth-arrested BL cells, EBNA-1 mRNA levels were twofold lower than in S phase, similar to the two- to eightfold differences in cell cycle expression of some cyclin mRNAs. Thus, although regulation of Qp is coupled to the cell cycle, this clearly has no impact on the level of EBNA-1 expressed in proliferating cells. We conclude, therefore, that the most important contribution of E2F to the regulation of Qp is to direct the pRb-mediated suppression of EBNA-1 expression within resting B cells, the principal reservoir of latent EBV. This would provide a means to restrict unneeded and potentially deleterious expression of EBNA-1 in a nonproliferating cell and to coordinate the activation of EBNA-1 expression necessary for EBV genome replication and maintenance upon reentry of the cell cycle in response to proliferative signals.
