Research

My research is focused on DNA replication and maintenance of Human papillomaviruses (HPVs) which infect the stratified epithelium of the genital tract. There are currently 20 million Americans infected with genital HPVs with 5.5 million new infections reported each year. While all genital HPVs possess the ability to induce benign warts, the high-risk HPVs (Types 16, 18, and 31 for example) are associated with an increased likelihood for progression of lesions to malignant cancer.

In their normal life cycle, HPVs exist as low-copy nuclear plasmids in the host basal epithelium where they can be maintained indefinitely. The viral life cycle is tightly linked to the differentiation program of the stratified epithelium, such that viral genome amplification only occurs in differentiated cells. Viral trans-acting factors, E1 and E2, play an important role in replication; E1, a helicase, recruits polymerase alpha to the origin of replication, while E2 acts cooperatively by binding and recruiting E1 to the origin of replication. E2 functions in two other important ways; by inducing transcription of viral genes, and by improving the inheritance of newly synthesized viral genomes to daughter cells. It is thought that E2 performs this function by tethering viral genomes to mitotic chromosomes, thus allowing accurate partitioning.

A major area of interest for my lab is the study of cis and trans-acting signals that control replication and maintenance of HPV genomes. We are currently investigating the role of E1 and E2 proteins in long-term replication during the viral lifecycle. We are also interested in determining the extent to which cellular factors influence stable replication of HPVs through the long control region (LCR).

In order to approach these studies, in addition to standard human cell culture, we are using a novel yeast-based system, which allows stable episomal replication of full-length HPV genomes (Angeletti et al. 2002 and Kim et al. 2005). The yeast/HPV system is powerful since it allows modeling of several HPV functions, including replication, transcription, and encapsidation. It provides a convenient means to assess the cis and trans-acting functions required for replication HPVs, as well as superior yeast genetic tools to determine the involvement of cellular genes in various viral functions. Using this system we are also currently investigating the physical parameters of HPV encapsidation (Angeletti, Methods in Molecular Medicine, 2005). Specifically, we are interested in how the viral factors E2 and L2 function in virion assembly and how they effect infectivity.

Another emerging interest of the lab is the investigation of HPV strains found in HIV positive patients in the sub-Saharan country of Zambia. In these studies we are investigating the prevalence of high-risk HPVs in Zambian patients and how HIV status and CD4 counts influence HPV-related disease; genital warts and dysplasias.