The Nuclear Chaperone Nucleophosmin Escorts an Epstein-Barr Virus Nuclear Antigen to Establish Transcriptional Cascades for Latent Infection in Human B Cells

Epstein-barr virus (ebv) is an oncogenic γ-herpesvirus that capably establishes both latent and lytic modes of infection in host cells and causes malignant diseases in humans. nuclear antigen 2 (ebna2)-mediated transcription of both cellular and viral genes is essential for the establishment and maintenance of the ebv latency program in b lymphocytes. here,we employed a protein affinity pull-down and lc-ms/ms analysis to identify nucleophosmin (npm1) as one of the cellular proteins bound to ebna2. additionally,the specific domains that are responsible for protein-protein interactions were characterized as ebna2 residues 300 to 360 and the oligomerization domain (od) of npm1. as in c-myc,dramatic npm1 expression was induced in ebv positively infected b cells after three days of viral infection,and both ebna2 and ebnalp were implicated in the transactivation of the npm1 promoter. depletion of npm1 with the lentivirus-expressed short-hairpin rnas (shrnas) effectively abrogated ebna2-dependent transcription and transformation outgrowth of lymphoblastoid cells. notably,the atp-bound state of npm1 was required to induce assembly of a protein complex containing ebna2,rbp-jκ,and npm1 by stabilizing the interaction of ebna2 with rbp-jκ. in a npm1-knockdown cell line,we demonstrated that an ebna2-mediated transcription defect was fully restored by the ectopic expression of npm1. our findings highlight the essential role of npm1 in chaperoning ebna2 onto the latency-associated membrane protein 1 (lmp1) promoters,which is coordinated with the subsequent activation of transcriptional cascades through rbp-jκ during ebv infection. these data advance our understanding of ebv pathology and further imply that npm1 can be exploited as a therapeutic target for ebv-associated diseases. © 2012 liu et al.