Nuclear factor-Y and Epstein Barr virus in nasopharyngeal cancer.
OBJECTIVE
The Epstein Barr virus (EBV) is intimately associated with nasopharyngeal cancer (NPC) in a latent state expressing a limited number of genes. The process of switching from latency to replication is not well understood, particularly in response to DNA stress; hence, the focus of this study is on an EBV-positive NPC model.


METHODS
C666-1 cells were exposed to radiation (2-15 Gy) or cisplatin (0.1-50 microg/mL) assayed subsequently for relative EBV copy number (BamHI) and lytic gene expression (BRLF1 and BZLF1) using quantitative real-time PCR. Chromatin immunoprecipitation was conducted to assess the interaction of the transcription factor nuclear factor-Y (NF-Y) with promoter sequences.


RESULTS
Radiation-induced and cisplatin-induced BamHI expression, along with increased levels of BRLF1 and BZLF1 in a dose-dependent and time-dependent manner, associated with the immediate nuclear transactivation of the transcription factor NF-Y and its own increased transcription of NF-Y subunits 8 h posttreatment. In silico analysis revealed three putative NF-Y consensus-binding sequences in the promoter region of BRLF1, which all interacted with NF-Y in response to radiation and cisplatin, confirmed using chromatin immunoprecipitation. Introduction of dominant-negative NF-YA reduced BRLF1 expression after radiation and cisplatin by 2.8-fold; in turn, overexpression of NF-YA resulted in a 2-fold increase in both BRLF1 and BZLF1 expression.


CONCLUSIONS
These results show that NF-Y is an important mediator of EBV stress response in switching from a latent to lytic state. This novel insight could provide a potential therapeutic strategy to enhance NPC response to radiation and cisplatin.
Chia
Marie C
MC
Department of Medical Biophysics, University of Toronto, Toronto, Canada.
Leung
Abby
A
Krushel
Tiffany
T
Alajez
Nehad M
NM
Lo
Kwok W
KW
Busson
Pierre
P
Klamut
Henry J
HJ
Bastianutto
Carlo
C
Liu
Fei-Fei
FF
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D023081:CCAAT-Binding Factor / Q000502:physiology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D020031:Epstein-Barr Virus Infections / Q000378:metabolism; D005720:Gamma Rays; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D015967:Gene Expression Regulation, Viral / Q000187:drug effects / Q000528:radiation effects; D005814:Genes, Viral; D004854:Herpesvirus 4, Human / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D051379:Mice; D016513:Mice, SCID; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000821:virology*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*; D014764:Viral Proteins / Q000378:metabolism; D014775:Virus Activation / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D017735:Virus Latency / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects
D000970:Antineoplastic Agents; C068382:BRLF1 protein, Human herpesvirus 4; C063676:BZLF1 protein, Herpesvirus 4, Human; D023081:CCAAT-Binding Factor; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014764:Viral Proteins; C402244:nuclear factor Y; D002945:Cisplatin