The Herpes Simplex Virus Immediate-Early Ubiquitin Ligase ICP0 Induces Degradation of the ICP0 Repressor Protein E2FBP1

E2FBP1/hDRIL1, a DNA-binding A/T-rich interaction domain (ARID) family transcription factor, is expressed ubiquitously in human tissues and plays an essential role in maintaining the proliferation potential of passage-limited human fibroblasts by dissociating promyelocytic leukemia nuclear bodies (PML-NBs). This effect on PML-NBs is similar to that of viral immediate-early gene products, such as infected cellular protein 0 (ICP0) from human herpes simplex virus 1 (HSV-1), which also disrupts PML-NBs to override the intrinsic cellular defense. Here we report that E2FBP1 inhibits accumulation of ICP0 RNA and, at the same time, is degraded via ICP0's herpes ubiquitin ligase 2 (HUL-2) activity upon HSV-1 infection. These reciprocal regulatory roles of ICP0 and E2FBP1 are linked in an ARID-dependent fashion. Our results suggest that E2FBP1 functions as an intrinsic cellular defense factor in spite of its PML-NB dissociation function.