Human papillomaviruses (HPV) are small DNA tumor viruses that are a significant cause of human disease, and nearly every cause of cervical cancer is caused by HPV. Initial infection with HPV is extremely cell-type specific and the normal replication cycle of HPV is tightly linked to the differentiation program of the host cell, but the cellular factors responsible for these links are not yet determined. I hypothesize that specific changes in the pattern of gene expression during cellular differentiation allow papillomavirus replication to progress. This project aims to identify these changes and to determine whether they are required to promote papillomavirus replication. Since HPV infection is directly linked to the development of cervical cancer, it is important to learn about the normal life cycle of this virus so that the altered viral functions that lead to disease can be understood. The first goal of the project is the definition and functional analysis of the state of chromatin modifications at human papillomavirus promoters in differentiated versus undifferentiated cells.
The second aim i s to identify and analyze cellular factors that are differentially expressed during cellular differentiation and allow human papillomavirus replication. The model system to be used consists of human keratinocytes that harbor the high-risk HPV31 genome as a multi-copy episome and can be induced to differentiate using specialized culture conditions. To understand how histone modifications at the two critical HPV promoters are different before and after keratinocyte differentiation, I will perform chromatin immunoprecipitations using antibodies directed against acetylated or methylated histones in undifferentiated versus differentiated cells. In complementary experiments, I will use microarray analysis to examine the changing pattern of cellular transcripts expressed in primary keratinocytes, with or without transfected viral genomes. I will study the genes and chromatin modifications of interest identified in these assayswith the goal of understanding which differentiation-mediated changes in expression are important in allowing the later stages of HPV gene expression and replication to occur.
This project is directly relevant to public health. The goal of the proposed experiments is to understand the basic biology of human papillomavirus, the cause of cervical cancer. This study will provide information about how human papillomavirus replicates and about how its replication could be blocked.
