Host microRNA-31-5p represses oncogenic herpesvirus lytic reactivation by restricting the RNA-binding protein KHDRBS3-mediated viral gene expression.

Oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV), an etiological agent of Kaposi's sarcoma and primary effusion lymphoma, employs a biphasic life cycle consisting of latency and lytic replication to achieve lifelong infection. Despite its essential role in KSHV persistence and tumorigenicity, much remains unknown about how KSHV lytic reactivation is regulated. Leveraging high-throughput transcriptomics, we identify microRNA-31-5p (miR-31-5p) as a key regulator of KSHV lytic reactivation capable of restricting KSHV entry into the lytic replication cycle. Ectopic expression of miR-31-5p impairs KSHV lytic gene transcription and production of lytic viral proteins, culminating in dramatic reduction of infectious virion production during KSHV reactivation. miR-31-5p overexpression also markedly reduces the expression of critical viral early genes, including the master regulator of the latent-lytic switch, KSHV replication and transcription activator (RTA) protein. Through mechanistic studies, we demonstrate that miR-31-5p represses KSHV lytic reactivation by directly targeting the KH domain protein KHDRBS3, an RNA-binding protein known to regulate RNA processing including alternative splicing. Our study highlights KHDRBS3 as an essential proviral host factor that is key to the successful completion of KSHV lytic replication and suggests its novel function in viral lytic gene transcription during KSHV reactivation. Taken together, these findings reveal a previously unrecognized role for the miR-31-5p/KHDRBS3 axis in regulating the KSHV latency-lytic replication switch and provide insights into gene expression regulation of lytic KSHV, which may be leveraged for lytic cycle-targeted therapeutic strategies against KSHV-associated malignancies.