TY  - GEN
N2  - An important initial step towards cervical cancer is the integration of HPV DNA copies into the host genome. Subsequently, the viral DNA gets targeted by methylation leading to its transcriptional silencing (Jeon et al., 1995; Yu et al., 2005). Later on, demethylation of these inserted HPV genomes correlates with further progression of cervical cancer (Badal et al., 2003). Therefore, characterisation of epigenetic mechanisms involved in oncogene re-expression is required to potentially counteract cancer development. In this study, the contribution of both epigenetic mechanisms, DNA demethylation and incorporation of histone variant H3.3 for the re-activation of the viral DNA transcription was analyzed. The cervical cancer cell line CaSki harbors approximately 600 mostly methylated HPV-16 copies and provides an excellent in vitro model to study epigenetic mechanisms in the context of HPV induced carcinogenesis. DNA demethylation was induced by treatment of these cells with 5-Desoxy-Azacytidine (DAC), which led to demethylation of approximately 50% of the silent HPV-16 copies. In addition, clones stably expressing a Myc-tagged H3.3 were generated and characterized in combination with DAC treatment. On protein level, DAC treatment of CaSki cells was accompanied by an unexpected down-regulation of the oncoprotein E7, where intracellular half life was rescued after exposure to proteosomal and calpain inhibitors. Additionally, for the first time, an interaction of E7 with, the transcription activating histone arginine methyltransferase, CARM1 was detected after E7-IP by Mass Spectrometry and Western blot. On transcriptional level, a slightly down-regulation of the E7 oncogene was detectable after DAC treatment of CaSki cells. Importantly, the same treatment induced E7 transcription in CaSki clones expressing Myc-H3.3, which was verified by both qPCR and Northern blot. In summary, this study demonstrates that DAC treatment induces down-regulation of oncoprotein E7 in CaSki cells. In addition, the data imply that DNA demethylation alone is not sufficient for re-activation of silent HPV genomes, since induction of E7 transcription strictly requires both, DNA demethylation and incorporation of the histone variant H3.3 into the URR of HPV-16.
A1  - Csernok, Andreea Iulia
KW  - HPV-16 
KW  -  Histone 
KW  -  5-Desoxy-Azacytidine (DAC)Epigenetic 
KW  -  Histone 
KW  -  5-Desoxy-Azacytidine (DAC) 
KW  -  HPV-16 
KW  -  cervical cancer
AV  - public
TI  - Identification of epigenetic mechanisms involved in transcriptional activation of silent HPV-16 genomes
ID  - heidok8431
Y1  - 2008///
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/8431/
ER  -