Persistent infection with high-risk human papillomaviruses (HPVs) is the major risk factor associated with cervical cancer, a disease that remains a leading cause of cancer death in women in the developing world. Although preneoplastic lesions can be detected by effective screening programs, some lesions are missed and the treatment of the other lesions causes morbidity and is a significant public health cost. The viral oncoproteins, E6 and E7 contribute directly to neoplasia by promoting unscheduled growth of suprabasal cells, disrupting cell cycle checkpoints that normally block replication or mitosis of damaged cells, blocking apoptosis, and activating telomerase. The resulting genetic instability allows the accumulation of numerous cellular changes that promote invasive and metastatic growth. Alterations in growth-promoting pathways such as mutations in RAS and over expression of c-MYC are seen in a substantial fraction of cervical cancers. The mechanisms by which E6 and E7 function are incompletely understood, as is the cross-talk between HPV and the other growth pathways. This application has three specific aims: 1) to determine the mechanism by which E6 activates the transcription of h-tert. We will investigate how E6 recruits histone acetyltransferases (HATs) to the h-tert promoter, either to c-MYC, or to a newly identified activator, and conversely how E6 displaces a newly identified repressor that may associate with histone deacetylases (HDACs). We have shown that E6AP is required for E6-induction of h-tert transcription, using shRNAs, and will examine whether the ubiquitin ligase function of E6AP is required. 2) To determine the contribution of hTERT, RAS and c-MYC to HPV associated neoplasia. We hypothesize that the activation of telomerase provides a growth advantage, and have shown that hTERT and RAS can synergize to promote transformed properties. We will investigate the activities of hTERT and RAS that are required and identify genes that are involved. We will determine whether c-MYC cooperates with HPV oncogenes to promote neoplasia. 3) Identify the substrates for E6AP and identify new ubiquitin ligases that interact with E6. We will use both shRNA to E6AP and dominant - negative E6AP combined with ICAT TM proteomics to identify new E6-dependent and independent targets of E6AP. We will test both candidate E3 ligases and other approaches to find new E6-associated ligases. Taken together these studies should provide a better understanding of HPV associated neoplasia.
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