ABSTRACT
Lytic infection by the Epstein-Barr virus (EBV) poses numerous health risks, such as infectious mononucleosis and lymphoproliferative disorder. Proteins in the bromodomain and extraterminal (BET) family regulate multiple stages of viral life cycles and provide promising intervention targets. Synthetic small molecules can bind to the bromodomains and disrupt function by preventing recognition of acetylated lysine substrates. We demonstrate that JQ1 and other BET inhibitors block two different steps in the sequential cascade of the EBV lytic cycle. BET inhibitors prevent expression of the viral immediate-early protein BZLF1. JQ1 alters transcription of genes controlled by the host protein BACH1, and BACH1 knockdown reduces BZLF1 expression. BET proteins also localize to the lytic origin of replication (OriLyt) genetic elements, and BET inhibitors prevent viral late gene expression. There JQ1 reduces BRD4 recruitment during reactivation to preclude replication initiation. This represents a rarely observed dual mode of action for drugs.
Subject(s)
Antiviral Agents/pharmacology , Basic-Leucine Zipper Transcription Factors/antagonists & inhibitors , Fanconi Anemia Complementation Group Proteins/antagonists & inhibitors , Gene Expression Regulation, Viral/drug effects , Herpesvirus 4, Human/drug effects , Nuclear Proteins/antagonists & inhibitors , Trans-Activators/antagonists & inhibitors , Transcription Factors/antagonists & inhibitors , Viral Proteins/antagonists & inhibitors , Acetylation , Azepines/pharmacology , Basic-Leucine Zipper Transcription Factors/chemistry , Basic-Leucine Zipper Transcription Factors/genetics , Basic-Leucine Zipper Transcription Factors/metabolism , Cell Cycle Proteins , Cell Line , Fanconi Anemia Complementation Group Proteins/chemistry , Fanconi Anemia Complementation Group Proteins/genetics , Fanconi Anemia Complementation Group Proteins/metabolism , Herpesvirus 4, Human/physiology , Host-Pathogen Interactions/drug effects , Humans , Lysine/metabolism , Nuclear Proteins/chemistry , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Protein Interaction Domains and Motifs , Protein Processing, Post-Translational , Protein Transport/drug effects , RNA Interference , Replication Origin/drug effects , Trans-Activators/chemistry , Trans-Activators/genetics , Trans-Activators/metabolism , Transcription Factors/chemistry , Transcription Factors/genetics , Transcription Factors/metabolism , Triazoles/pharmacology , Viral Proteins/chemistry , Viral Proteins/genetics , Viral Proteins/metabolism , Virus Activation/drug effects , Virus Physiological Phenomena/drug effectsABSTRACT
The human Epstein-Barr virus (EBV) evades the immune system by entering a transcriptionally latent phase in B cells. EBV in tumor cells expresses distinct patterns of genes referred to as latency types. Viruses in tumor cells also display varying levels of lytic transcription resulting from spontaneous reactivation out of latency. We measured this dynamic range of lytic transcription with RNA deep sequencing and observed no correlation with EBV latency types among genetically different viruses, but type I cell lines reveal more spontaneous reactivation than isogenic type III cultures. We further determined that latency type and spontaneous reactivation levels predict the relative amount of induced reactivation generated by cytotoxic chemotherapy drugs. Our work has potential implications for personalizing medicine against EBV-transformed malignancies. Identifying latency type or measuring spontaneous reactivation may provide predictive power in treatment contexts where viral production should be either avoided or coerced.
