Human herpesvirus 8 interferon regulatory factors 1 and 3 mediate replication and latency activities via interactions with USP7 deubiquitinase

Qiwang Xiang, Hyunwoo Ju, Qian Li, Szu Chieh Mei, Daming Chen, Young Bong Choi, John Nicholas

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Human herpesvirus 8 (HHV-8) encodes four viral interferon regulatory factors (vIRF-1 to -4) that likely function to suppress innate immune and cellular stress responses through inhibitory interactions with various cellular proteins involved in these activities. It is notable that vIRF-1 and -4 have been reported to interact with the deubiquitinase ubiquitin-specific protease 7 (USP7), substrates of which include p53 and the p53-targeting and -destabilizing ubiquitin E3 ligase MDM2. Structural studies of vIRF-1 and vIRF-4 USP7 binding sequences in association with USP7 have been reported; both involve interactions with N-terminal-domain residues of USP7 via EGPS and ASTS motifs in vIRF-1 and vIRF-4, respectively, but vIRF-4 residues also contact the catalytic site. However, the biological activities of vIRF-1 and vIRF-4 via USP7 interactions are unknown. Here, we report that vIRF-3, which is latently, as well as lytically, expressed in HHV-8-infected primary effusion lymphoma (PEL) cells, also interacts with USP7- via duplicated EGPS motifs-and that this interaction is important for PEL cell growth and viability. The interaction also contributes to suppression of productive virus replication by vIRF-3, which we identify here. We further show that vIRF-1, which is expressed at low levels in PEL latency, promotes latent PEL cell viability and that this activity and vIRF-1-promoted productive replication (reported previously) involve EGPS motif-mediated USP7 targeting by vIRF-1. This study is the first to identify latent and lytic functions of vIRF-1 and vIRF-3, respectively, and to address the biological activities of these vIRFs through their interactions with USP7.

Original languageEnglish (US)
Article numbere02003-17
JournalJournal of virology
Issue number7
StatePublished - Apr 1 2018


  • Human herpesvirus 8
  • Latency
  • Lytic replication
  • USP7
  • Viral interferon regulatory factors

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology


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