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oai:www.ideals.illinois.edu:2142/84827 2023-07-11 col_2142_5131 col_2142_14795 com_2142_5130 com_2142_14794 com_2142_14793 com_2142_8903

Cheng-Ming Chiang Thomas, Mary C. 2015-09-25T22:28:05Z 2015-09-25T22:28:05Z 10000-01-01 2006 2006 The mechanism employed by DNA tumor viruses to inhibit p53-dependent transcription is poorly understood. Here we describe a new paradigm for human papillomavirus (HPV) E6 oncoprotein-mediated repression of human p21 WAF1 cyclin-dependent kinase inhibitor gene transcription, independent of its well known role to promote the ubiquitination and degradation of p53. Using both high-risk and low-risk HPV E6 oncoproteins, each representing a class of oncoproteins that is capable of inducing p53 degradation or unable to degrade p53, respectively, we investigated whether these DNA tumor viruses shared a general repression mechanism to inhibit p53-target gene transcription. We used UV-irradiated human fibrosarcoma HT1080 cells treated with proteasome inhibitors (MG132) and in vitro-assembled chromatin templates reconstituted with purified chromatin assembly factors (Acf1 and ISWI), core histones (H2A, H2B, H3, and H4), and a histone chaperone (NAP-1) in order to define the mechanism used by high-risk and low-risk HPV E6 to inhibit p53-dependent transcription. We demonstrate that E6 does not prevent p53 or p300 recruitment to the chromatin, but inhibits p300-mediated acetylation on p53 and nucleosomal core histones. This suppression of protein acetylation requires the E6-interacting regions of p300. Moreover, high-risk HPV E6 mutants unable to interact with p53 or p300, but not deficient in inducing p53 degradation, fail to inhibit p53-mediated activation in vitro and in vivo, indicating that a p53-E6-p300-containing protein complex is critical for repressing p53-target gene activation. It is likely that this mechanism for repressing p53 target gene transcription is common among DNA tumor viruses based on the finding that SV40 large T-antigen, polyomavirus large T-antigen, adenovirus E1B 19K, and human papillomavirus E6 encoded-oncoproteins inhibited p53-dependent chromatin transcription at a step prior to the entry of p300, indicating that oncoprotein incorporation into p53-p300 complex constitutes a major switch for virus-mediated gene regulation through modulation of p300-targeted acetylation on p53 and nucleosomal core histones. Made available in DSpace on 2015-09-25T22:28:05Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3223732.pdf: 8063588 bytes, checksum: adf647406acf78d7fb9f7e227701080a (MD5) Previous issue date: 2006 Embargo set by: Seth Robbins for item 86108 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs U of I Only 255 p. Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. http://hdl.handle.net/2142/84827 (MiAaPQ)AAI3223732 eng Health Sciences, Oncology Mechanism of Human Papillomavirus E6-Mediated Repression of P53-Target Gene *Transcription text Biochemistry Biochemistry University of Illinois at Urbana-Champaign Dissertation Ph.D.