Nuclear translocation of Sp100A suppresses multiple DNA viruses and limits HSV-1 lytic replication in vivo.

Sp100 (Speckled protein 100 kDa), a key component of promyelocytic leukemia (PML) nuclear bodies, plays a pivotal role in intrinsic and innate immunity. The predominant isoform, Sp100A, has been shown by our previous studies to shuttle between subcellular compartments to enhance innate immunity against RNA viruses and to circulate between cells via extracellular vesicles (EVs) to restrict herpes simplex virus 1 (HSV-1) spread. This study investigates the biological significance of the cyto-nuclear shuttling of Sp100A, a key component of PML nuclear bodies, in antiviral defense against DNA viruses, particularly herpes simplex virus 1 (HSV-1). We demonstrate that Sp100A effectively inhibits multiple DNA viruses in vitro, with its antiviral activity being critically regulated by phosphorylation at the S188 site (a nuclear import-mimicking mutant, S188D, is active, while the S188A mutant is not). Furthermore, DNA virus infection and type I IFN significantly induce Sp100A secretion via extracellular vesicles (EVs), which confers broad, non-IFN-mediated antiviral protection between cells. In a murine model, Sp100A expression significantly reduced HSV-1 lytic replication and clinical signs, but did not impair latency establishment or reactivation potential. These findings underscore the critical role of Sp100A's dynamic shuttling in antiviral defense, showing its activity is specifically restricted to the lytic phase of HSV-1. Sp100A's multifaceted antiviral properties highlight its potential as a novel therapeutic target for combating DNA virus infections.