Proteomic screening identifies HNRNPA2B1 as an epigenetic repressor of Epstein-Barr virus reactivation.

Epstein-Barr virus (EBV) establishes lifelong persistent infection in over 90% of the world's population. The virus persists as an episome in the host cells during latency and periodically reactivates through transcriptional activation of the immediate-early (IE) genes. While epigenetic regulation is central to maintaining viral latency, the host factors that enforce repression at these promoters remain incompletely defined. Here, we employed a novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9-based engineered DNA-binding molecule-mediated chromatin immunoprecipitation coupled with mass spectrometry (enChIP-MS) approach to identify proteins associated with the promoter of EBV IE gene ZTA. This approach revealed an enrichment of multiple heterogeneous nuclear ribonucleoproteins and identified HNRNPA2B1 as a potential regulator of EBV ZTA gene expression. Functional analyses across multiple EBV+ cancer cell models demonstrated that HNRNPA2B1 acts as a restriction factor for EBV lytic reactivation. Depletion of HNRNPA2B1 led to increased expression of IE and downstream lytic genes, enhanced RNA polymerase II recruitment to the ZTA and RTA promoters, and elevated the proportion of cells entering the lytic cycle. Conversely, enforced expression of HNRNPA2B1 suppressed EBV lytic reactivation. Mechanistically, HNRNPA2B1 enhances repressive viral chromatin states by facilitating recruitment of the histone demethylase LSD1 to EBV IE gene promoters, thereby limiting the activating histone H3 lysine 4 trimethylation. Together, these findings identify HNRNPA2B1 as a key epigenetic regulator of EBV latency and link RNA-binding proteins to epigenetic control of viral reactivation.IMPORTANCEThis study identifies HNRNPA2B1 as a previously unrecognized host factor that promotes Epstein-Barr virus (EBV) latency through direct regulation of viral chromatin at immediate-early gene promoters. By integrating locus-specific chromatin proteomics with functional and mechanistic analyses, our work reveals how an RNA-binding protein HNRNPA2B1 recruits a histone-modifying enzyme to control EBV reactivation. These findings provide new insights into host-virus interactions that control EBV latency and reactivation and highlight the role of RNA-binding proteins in chromatin regulation that may be broadly relevant to other latent DNA viruses.