Gene expression and transcription factor profiling reveal inhibition of transcription factor cAMP-response element-binding protein by gamma-herpesvirus replication and transcription activator.

Herpesvirus replication involves the expression of over 80 viral genes in a well ordered sequence, leading to the production of new virions. Viral genes expressed during the earliest phases of replication often regulate both viral and cellular genes. Therefore, they have the potential to bring about dramatic functional changes within the cell. Replication and transcription activator (RTA) is a potent immediate early transcription activator of the gamma-herpesvirus family. This family includes Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus, human pathogens associated with malignancy. Here we combine gene array technology with transcription factor profiling to identify the earliest DNA promoter and cellular transcription factor targets of RTA in the cellular genome. We find that expression of RTA leads to both activation and inhibition of distinct groups of cellular genes. The identity of the target genes suggests that RTA rapidly changes the cellular environment to counteract cell death pathways, support growth factor signaling, and also promote immune evasion of the infected cell. Transcription factor profiling of the target gene promoters highlighted distinct pathways involved in gene activation at specific time points. Most notable throughout was the high level of cAMP-response element-binding protein (CREB)-response elements in RTA target genes. We find that RTA can function as either an activator or an inhibitor of CREB-response genes, depending on the promoter context. The association with CREB also highlights a novel connection and coordination between viral and cellular "immediate early" responses.