X-linked RNA-binding motif protein (RBMX) is required for the maintenance of Borna disease virus nuclear viral factories.

Borna disease virus (BDV) is a non-segmented, negative-strand RNA virus that establishes persistent infection in the nucleus. Although BDV forms viral inclusion bodies, termed viral speckles of transcripts (vSPOTs), which are associated with chromatin in the nucleus, the host factors involved in the maintenance of vSPOTs remain largely unknown. In this study, we identified X-linked RNA-binding motif protein (RBMX) as a nuclear factor interacting with BDV nucleoprotein. Interestingly, knockdown of RBMX led to disruption of the formation of vSPOTs and reduced both transcription and replication of BDV. Our results indicate that RBMX is involved in the maintenance of the structure of the virus factory in the nucleus.