{"id":{"repo_id":"birmingham","oai_identifier":"oai:etheses.bham.ac.uk:823"},"canonical_url":"https://search.dev.ndltd.org/etd/birmingham/oai:etheses.bham.ac.uk:823","repository":{"repo_id":"birmingham","name":"University of Birmingham","base_url":"https://etheses.bham.ac.uk/cgi/oai2"},"display":{"title":"An investigation of post-translational modification of human papillomavirus E4 and the role of modified E4 proteins during the virus life cycle","abstract":"Infection with human papillomaviruses (HPV) is the etiological basis for cervical cancer. The HPV E1^E4 protein is proposed to be a major regulator of the HPV life cycle and the multiple and diverse activities associated with E1^E4 suggest that it is a multi-functional protein. This thesis has sought to address the hypothesis that phosphorylation and proteolysis contribute towards the pleiotrophic functions of the E1^E4 protein, and has investigated the functional significance of these E1^E4 post-translational modifications during the HPV life cycle. This study has uncovered the novel finding that the E1^E4 protein of HPV type 18 (HPV18) exists as a phospho-protein within cells and is a substrate for multiple cellular kinases in vitro. The phospho-acceptor residue for cyclin-dependent kinases (CDK) 1 and 2 has been identified as threonine 23, whilst serine 58 is phosphorylated by protein kinase A (PKA). Furthermore, a cyclin binding motif (\\(^{43}\\)RRL\\(^{45}\\)) within the HPV18 E1^E4 protein is required for association with active CDK complexes and this association may influence CDK activity since the activity of CDK2-cyclin A was shown to be reduced in the presence of HPV18 E1^E4. This thesis has revealed that HPV18 E1^E4 is a target for N-terminal proteolysis, and this post-translational modification occurs during the HPV18 replication cycle. Key elements necessary for proteolysis have been mapped to a conserved leucine-rich sequence (LLXLL) present at the N-terminus of the HPV18 E1^E4 protein. Since E1^E4 expression is required for HPV18 genome amplification, N-terminally truncated E4 species may contribute towards its role in the replication cycle. To examine this hypothesis, mutations that attenuate E1^E4 proteolysis were introduced into HPV18 genomes and transfected into human foreskin keratinocytes (HFK). Mutation of the leucine-rich motif prevented efficient proteolysis of the E1^E4 protein during the HPV life cycle and resulted in reduced viral genome amplification within differentiating HFKs suggesting that efficient E1^E4 proteolysis may be required for this E4 function.","abstract_html":"Infection with human papillomaviruses (HPV) is the etiological basis for cervical cancer. The HPV E1^E4 protein is proposed to be a major regulator of the HPV life cycle and the multiple and diverse activities associated with E1^E4 suggest that it is a multi-functional protein. This thesis has sought to address the hypothesis that phosphorylation and proteolysis contribute towards the pleiotrophic functions of the E1^E4 protein, and has investigated the functional significance of these E1^E4 post-translational modifications during the HPV life cycle. This study has uncovered the novel finding that the E1^E4 protein of HPV type 18 (HPV18) exists as a phospho-protein within cells and is a substrate for multiple cellular kinases in vitro. The phospho-acceptor residue for cyclin-dependent kinases (CDK) 1 and 2 has been identified as threonine 23, whilst serine 58 is phosphorylated by protein kinase A (PKA). Furthermore, a cyclin binding motif (<span class=\"etd-inline-math\"><sup>43</sup></span>RRL<span class=\"etd-inline-math\"><sup>45</sup></span>) within the HPV18 E1^E4 protein is required for association with active CDK complexes and this association may influence CDK activity since the activity of CDK2-cyclin A was shown to be reduced in the presence of HPV18 E1^E4. This thesis has revealed that HPV18 E1^E4 is a target for N-terminal proteolysis, and this post-translational modification occurs during the HPV18 replication cycle. Key elements necessary for proteolysis have been mapped to a conserved leucine-rich sequence (LLXLL) present at the N-terminus of the HPV18 E1^E4 protein. Since E1^E4 expression is required for HPV18 genome amplification, N-terminally truncated E4 species may contribute towards its role in the replication cycle. To examine this hypothesis, mutations that attenuate E1^E4 proteolysis were introduced into HPV18 genomes and transfected into human foreskin keratinocytes (HFK). Mutation of the leucine-rich motif prevented efficient proteolysis of the E1^E4 protein during the HPV life cycle and resulted in reduced viral genome amplification within differentiating HFKs suggesting that efficient E1^E4 proteolysis may be required for this E4 function.","abstract_has_math":true,"creators":["Pugh, Alice Georgia"],"institution":"University of Birmingham","degree_name":"d_ph","degree_level":"d_ph","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010-07","date_published":"2010-07","updated_at":"2026-07-24T01:11:10Z","subjects":["R Medicine (General)","RC0254 Neoplasms. Tumors. Oncology (including Cancer)"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.sponsor","label":"Sponsor","values":["cancer_research_uk"]},{"key":"dc:creator","label":"Author","values":["Pugh, Alice Georgia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2010-07"]},{"key":"dc:date.issued","label":"Date","values":["2010-07"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["College of Medical & Dental Sciences","Institute of Cancer Studies"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Birmingham"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["http://etheses.bham.ac.uk//id/eprint/823/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["d_ph"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["d_ph"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["R Medicine (General)","RC0254 Neoplasms. Tumors. Oncology (including Cancer)"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://etheses.bham.ac.uk//id/eprint/823/1/Pugh10PhD.pdf","http://etheses.bham.ac.uk//id/eprint/823/2/Decl_IS_Pugh10PhD.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Infection with human papillomaviruses (HPV) is the etiological basis for cervical cancer. The HPV E1^E4 protein is proposed to be a major regulator of the HPV life cycle and the multiple and diverse activities associated with E1^E4 suggest that it is a multi-functional protein. This thesis has sought to address the hypothesis that phosphorylation and proteolysis contribute towards the pleiotrophic functions of the E1^E4 protein, and has investigated the functional significance of these E1^E4 post-translational modifications during the HPV life cycle. This study has uncovered the novel finding that the E1^E4 protein of HPV type 18 (HPV18) exists as a phospho-protein within cells and is a substrate for multiple cellular kinases in vitro. The phospho-acceptor residue for cyclin-dependent kinases (CDK) 1 and 2 has been identified as threonine 23, whilst serine 58 is phosphorylated by protein kinase A (PKA). Furthermore, a cyclin binding motif (\\(^{43}\\)RRL\\(^{45}\\)) within the HPV18 E1^E4 protein is required for association with active CDK complexes and this association may influence CDK activity since the activity of CDK2-cyclin A was shown to be reduced in the presence of HPV18 E1^E4. This thesis has revealed that HPV18 E1^E4 is a target for N-terminal proteolysis, and this post-translational modification occurs during the HPV18 replication cycle. Key elements necessary for proteolysis have been mapped to a conserved leucine-rich sequence (LLXLL) present at the N-terminus of the HPV18 E1^E4 protein. Since E1^E4 expression is required for HPV18 genome amplification, N-terminally truncated E4 species may contribute towards its role in the replication cycle. To examine this hypothesis, mutations that attenuate E1^E4 proteolysis were introduced into HPV18 genomes and transfected into human foreskin keratinocytes (HFK). Mutation of the leucine-rich motif prevented efficient proteolysis of the E1^E4 protein during the HPV life cycle and resulted in reduced viral genome amplification within differentiating HFKs suggesting that efficient E1^E4 proteolysis may be required for this E4 function."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["An investigation of post-translational modification of human papillomavirus E4 and the role of modified E4 proteins during the virus life cycle"]}]}],"canonical_facts":{"dc:contributor.sponsor":["cancer_research_uk"],"dc:creator":["Pugh, Alice Georgia"],"dc:date":["2010-07"],"dc:date.issued":["2010-07"],"dc:description.abstract":["Infection with human papillomaviruses (HPV) is the etiological basis for cervical cancer. The HPV E1^E4 protein is proposed to be a major regulator of the HPV life cycle and the multiple and diverse activities associated with E1^E4 suggest that it is a multi-functional protein. This thesis has sought to address the hypothesis that phosphorylation and proteolysis contribute towards the pleiotrophic functions of the E1^E4 protein, and has investigated the functional significance of these E1^E4 post-translational modifications during the HPV life cycle. This study has uncovered the novel finding that the E1^E4 protein of HPV type 18 (HPV18) exists as a phospho-protein within cells and is a substrate for multiple cellular kinases in vitro. The phospho-acceptor residue for cyclin-dependent kinases (CDK) 1 and 2 has been identified as threonine 23, whilst serine 58 is phosphorylated by protein kinase A (PKA). Furthermore, a cyclin binding motif (\\(^{43}\\)RRL\\(^{45}\\)) within the HPV18 E1^E4 protein is required for association with active CDK complexes and this association may influence CDK activity since the activity of CDK2-cyclin A was shown to be reduced in the presence of HPV18 E1^E4. This thesis has revealed that HPV18 E1^E4 is a target for N-terminal proteolysis, and this post-translational modification occurs during the HPV18 replication cycle. Key elements necessary for proteolysis have been mapped to a conserved leucine-rich sequence (LLXLL) present at the N-terminus of the HPV18 E1^E4 protein. Since E1^E4 expression is required for HPV18 genome amplification, N-terminally truncated E4 species may contribute towards its role in the replication cycle. To examine this hypothesis, mutations that attenuate E1^E4 proteolysis were introduced into HPV18 genomes and transfected into human foreskin keratinocytes (HFK). Mutation of the leucine-rich motif prevented efficient proteolysis of the E1^E4 protein during the HPV life cycle and resulted in reduced viral genome amplification within differentiating HFKs suggesting that efficient E1^E4 proteolysis may be required for this E4 function."],"dc:format":["application/pdf"],"dc:identifier.uri":["http://etheses.bham.ac.uk//id/eprint/823/1/Pugh10PhD.pdf","http://etheses.bham.ac.uk//id/eprint/823/2/Decl_IS_Pugh10PhD.pdf"],"dc:publisher.department":["College of Medical & Dental Sciences","Institute of Cancer Studies"],"dc:publisher.institution":["University of Birmingham"],"dc:relation.isreferencedby":["http://etheses.bham.ac.uk//id/eprint/823/"],"dc:subject":["R Medicine (General)","RC0254 Neoplasms. Tumors. 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