Determination of minimum herpes simplex virus type 1 components necessary to localize transcriptionally active DNA to ND10.

DNA viruses such as herpes simplex virus type 1 (HSV-1) appear to start their replicative processes at specific nuclear domains known as ND10. In analyses to determine the minimum viral components needed for transcript accumulation at ND10, we find that a specific viral DNA sequence, OriS, and the viral immediate-early proteins ICP4 and ICP27 are sufficient for a reporter gene placed in cis to the OriS sequence to transcribe at ND10. A chromatin immunoprecipitation assay demonstrated expected critical intermediates in retaining the minimal genome at ND10 for the HSV-1 replication origin through direct or indirect binding to the host protein Daxx. Coimmunoprecipitation assays with antibodies to Daxx and ICP4, ICP27, and ICP8 showed that the respective proteins interact, possibly forming a complex. A potential complex between the origin, early viral DNA-binding protein ICP8 and Daxx did not result in transcription at ND10. Thus, the deposition of transcriptionally active HSV-1 genomes at ND10 is most likely a consequence of retention at ND10 through the interaction of viral genome-bound ICP4 and ICP27 with Daxx. Such a complex might be more likely immobilized at the outside of ND10 by the PML-interacting Daxx than at other nuclear sites.