Epigenetic silencing of interferon-kappa in human papillomavirus type 16-positive cells.
We have investigated interferon-kappa (IFN-kappa) regulation in the context of human papillomavirus (HPV)-induced carcinogenesis using primary human foreskin keratinocytes (HFK), immortalized HFKs encoding individual oncoproteins of HPV16 (E6, E7, and E6/E7), and cervical carcinoma cells. Here, IFN-kappa was suppressed in the presence of E6, whereas its expression was not affected in HFKs or E7-immortalized HFKs. Transcription could be reactivated after DNA demethylation but was decreased again upon drug removal. Partial reactivation could also be accomplished when E6 was knocked down, suggesting a contribution of E6 in IFN-kappa de novo methylation. We identified a single CpG island near the transcriptional start site as being involved in selective IFN-kappa expression. To prove the functional relevance of IFN-kappa in building up an antiviral response, IFN-kappa was ectopically expressed in cervical carcinoma cells where protection against vesicular stomatitis virus-mediated cytolysis could be achieved. Reconstitution of IFN-kappa was accompanied by an increase of p53, MxA, and IFN-regulatory factors, which was reversed by knocking down either IFN-kappa or p53 by small interfering RNA. This suggests the existence of a positive feedback loop between IFN-kappa, p53, and components of IFN signaling pathway to maintain an antiviral state. Our in vitro findings were further corroborated in biopsy samples of cervical cancer patients, in which IFN-kappa was also downregulated when compared with normal donor tissue. This is the first report showing an epigenetic silencing of type I IFN after HPV16 oncogene expression and revealing a novel strategy on how high-risk HPVs can abolish the innate immune response in their genuine host cells.
Rincon-Orozco
Bladimiro
B
Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Universität Heidelberg, Heidelberg, Germany.
Halec
Gordana
G
Rosenberger
Simone
S
Muschik
Dorothea
D
Nindl
Ingo
I
Bachmann
Anastasia
A
Ritter
Tina Maria
TM
Dondog
Bolormaa
B
Ly
Regina
R
Bosch
Franz X
FX
Zawatzky
Rainer
R
Rösl
Frank
F
D015153:Blotting, Western; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D015536:Down-Regulation; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D020868:Gene Silencing / Q000502:physiology*; D052162:Human papillomavirus 16 / Q000276:immunology; D006801:Humans; D007370:Interferon Type I / Q000096:biosynthesis / Q000235:genetics*; D015603:Keratinocytes / Q000821:virology; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis / Q000235:genetics; D030361:Papillomavirus Infections / Q000150:complications / Q000235:genetics*; D034741:RNA, Small Interfering; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000821:virology
C068651:E6 protein, Human papillomavirus type 16; D007370:Interferon Type I; D009856:Oncogene Proteins, Viral; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C439669:interferon kappa