{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/84827"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/84827","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Mechanism of Human Papillomavirus E6-Mediated Repression of P53-Target Gene *Transcription","abstract":"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.","abstract_html":"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.","abstract_has_math":false,"creators":["Thomas, Mary C."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Biochemistry","degree_department":null,"school":null,"contributors":["Cheng-Ming Chiang"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T22:28:05Z","date_published":"2015-09-25T22:28:05Z","updated_at":"2026-07-22T22:26:24Z","subjects":["Health Sciences, Oncology"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3223732"],"render_values":[{"text":"(MiAaPQ)AAI3223732","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/84827","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Cheng-Ming Chiang"]},{"key":"dc:creator","label":"Author","values":["Thomas, Mary C."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T22:28:05Z","10000-01-01","2006"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biochemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Health Sciences, Oncology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/84827","(MiAaPQ)AAI3223732"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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). 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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). 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