Human papillomaviruses (HPV) are the causative agents of different clinical types of skin warts and genital proliferations corresponding to the most common sexually transmitted infection. In addition, certain HPV induced carcinoma of the uterine cervix (HPV 16 and HPV18), the second woman cancer worldwide, and of the skin (HPV5) in patients suffering from epidermodysplasia verruciformis (EV). This genodermatosis results from mutations in either of two adjacent genes (EVER1and EVER2) that confer predisposition to infection with a specific group of viruses (beta-HPV), including HPV5. Defects in immunosurveillance of the infection with beta-HPV are observed in the disease. Our aims are to better characterize the functions of EVER1 and EVER2 proteins in normal and infected cells and to analyze the role of viral early proteins (E2, E5, E6 and E7) in the HPV life cycle and in the malignant transformation associated with oncogenic HPV.

EVER protein functions.

We have demonstrated that EVER1 and EVER2 form a complex in the endoplasmic reticulum with the zinc transporter ZnT-1. This complex is involved in the maintenance of cellular zinc homeostasis and plays a central role in HPV-specific protective mechanisms as a negative regulator of some cellular transcription factors (c-Jun, c-Fos) needed for viral genome expressionand replication. Deregulation of cellular zinc balance emerges as an important step in the life cycle of not only cutaneous beta-HPV but also genital alpha-HPV. Recent data suggest that beta-HPV are defective viruses expressed during epidermal repair processes and favor cell proliferation during wound healing. As far as the impact of EVER proteins on the control of immune response is concerned, we have demonstrated that a defect in EVER2 expression results in decreased secretion of IL-6. EVER2 was found to play an important role in the regulation of NF-κB and AP-1 signaling pathways in keratinocytes.

Role of early proteins in HPV life cycle and cell transformation

It is currently assumed that the pathogenesis of HPV results from complex viral and host factor relationships driven in particular by the interplay between the host proteome and the early viral proteins E5, E6 and E7 but also from deregulation by the viral protein E2. Our goal is mainly focused on the characterization of viral protein activities specifically required to initiate and complete HPV life cycle (latency, replication, maturation) and to identify biological properties of early proteins associated with oncogenic potential. We have develop a new comparative interactomics approach, based on the overlapping yeast two-hybrid interactome profiles of early viral proteins from 12 reference cutaneous and mucosal HPV with distinct oncogenic potential. Validation of interactions was performed in mammalian cells by using a high-throughput protein-protein complementation assay (PCA). Biostatistical analyses of these datasets allowed to correlate specific virus-host interactions with pathological traits. We currently analyze the alteration of keratinocyte differentiation and regulation of the NF-κB signaling pathway by the E2 proteins of the 12 reference HPV. Similarly, we investigate the rewiring of the TGF-βpathway by the E6 protein of the oncogenic HPV5.

These approaches bring new insights into genetic control of HPV infection and shed new light on viral strategies involved in skin and genital carcinogenesis. Specific interactions between viral and cellular proteins may provide targets for drug design.

Keywords: Viral carcinogenesis, human papillomavirus (HPV), epidermodysplasia verruciformis, predisposition genes, control of HPV infection, biological properties of early viral proteins, viral and human interactomes, yeast two-hybrid screening, protein-protein complementation assay

Lazarczyk M, Pons C, Mendoza JA, Cassonnet P, Jacob Y, and Favre M. (2008). Regulation of cellular zinc balance as a potential mechanism of EVER-mediated protection against pathogenesis by cutaneous oncogenic human papillomaviruses.J. Exp. Med.205:35-42

Thierry F and Demeret C. (2008). Direct activation of caspase 8 by the proapoptotic E2 protein of HPV18 independent of adaptor proteins. Cell. Death Diff.15:1356-1363.

Lazarczyk M and Favre M. (2008). The role of Zn2+ ions in host-virus interactions. J. Virol.82:11486-11494.

Lazarczyk M, Cassonnet P, Pons C, Jacob Y, and Favre M. (2009). The EVER proteins as a natural barrier against papillomaviruses: a new insight into the pathogenesis of HPV infections. Microbiol. Mol. Biol. Rev.73:348-370.

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