Reversal of human cytomegalovirus major immediate-early enhancer/promoter silencing in quiescently infected cells via the cyclic AMP signaling pathway

Michael J. Keller, Allen W. Wu, Janet Andrews, Patrick W. McGonagill, Eric E. Tibesar, Jeffery L. Meier

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

The human cytomegalovirus (HCMV) major immediate-early (MIE) enhancer contains five functional cyclic AMP (cAMP) response elements (CRE). Because the CRE in their native context do not contribute appreciably to MIE enhancer/promoter activity in lytically infected human fibroblasts and NTera2 (NT2)-derived neurons, we postulated that they might have a role in MIE enhancer/promoter reactivation in quiescently infected cells. Here, we show that stimulation of the cAMP signaling pathway by treatment with forskolin (FSK), an adenylyl cyclase activator, greatly alleviates MIE enhancer/promoter silencing in quiescently infected NT2 neuronal precursors. The effect is immediate, independent of de novo protein synthesis, associated with the phosphorylation of ATF-1 serine 63 and CREB serine 133, dependent on protein kinase A (PKA) and the enhancer's CRE, and linked to viral-lytic-cycle advancement. Coupling of FSK treatment with the inhibition of either histone deacetylases or protein synthesis synergistically activates MIE gene expression in a manner suggesting that MIE enhancer/promoter silencing is optimally relieved by an interplay of multiple regulatory mechanisms. In contrast, MIE enhancer/promoter silence is not overcome by stimulation of the gamma interferon (IFN-γ) signaling pathway, despite the enhancer having two IFN-γ-activated-site-like elements. We conclude that stimulation of the cAMP/PKA signaling pathway drives CRE-dependent MIE enhancer/promoter activation in quiescently infected cells, thus exposing a potential mode of regulation in HCMV reactivation.

Original languageEnglish (US)
Pages (from-to)6669-6681
Number of pages13
JournalJournal of virology
Volume81
Issue number12
DOIs
StatePublished - Jun 2007

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