Biomedical Sciences ETDs

Hebin Song

Publication Date

12-1-2009

Abstract

Human papillomaviruses (HPVs) are small, non-enveloped double stranded DNA viruses that demonstrate a strict species and cell type tropism for human epithelial cells. The association between high-risk HPV types and cervical cancer is well established. Additionally, HPVs have been implicated as causes in development of several other epithelial cancer types. Increasing data indicate heat shock proteins (HSPs) including inducible HSP70 (HSP70i) are involved in the replicative cycles of different viruses including adenoviruses, polyomaviruses (PyV), and some RNA viruses. Cell-free system studies implicate HSP70i in HPV11 genome replication with E1 and E2 proteins, and there is evidence that HSP70 is involved in capsid assembly and disassembly for PyV and PV. HSP70 expression is increased in HPV16 E6/E7 gene transduced human primary keratinocytes, and frequently detected in early stage uterine cervical cancer at levels in conjunction with lesion severity. In this study we carry out analyses with the natural host cell to assess HSP70i's role in the viral infectious life cycle. For these studies we used the organotypic (raft) culture system to recapitulate the full viral life cycle of the high-risk human papillomavirus type 31 (HPV31). Upon heat shock of HPV31 infected organotypic tissues, we find high and sustained expression of HSP70i coincident with enhanced HPV genome replication and virion production. Whereas there is no detectable effect on total L1 expression levels, we find that HSP70i interacts with L1, colocalizes with and enhances L1 nuclear localization in differentiated cells. Adenovirus-mediated gene transfer was used to study the effects of HSP70i in naturally HPV infected differentiating tissues and showed results similar to those in heat shocked rafts. In HPV31 infected monolayer cells ectopically expressing viral capsid proteins, without obvious impact on L1 expression levels, our results suggest wild type HSP70i interacts with and promotes L1 translocation into nucleus concomitant with increased HPV genome replication and virion production. Alternatively, HSP70i ATPase domain mutant (HSP70i(K71A)) impedes virion production while viral genome levels, L1 expression and localization demonstrate the same pattern as control. These results indicate that HSP70i is involved in diverse aspects of the viral life cycle including genome replication, capsid protein transportation and virion morphogenesis. We conclude that HSP70i contributes directly to these HPV replicative viral activities and the production of infectious progeny virions.

Keywords

human papillomavirus, Heat shock protein, co-factors, chaperone, epithelium, virus morphogenesis, genital infection, cervical cancer

Document Type

Dissertation

Language

English

Degree Name

Biomedical Sciences

Level of Degree

Doctoral

Department Name

Biomedical Sciences Graduate Program

First Committee Member (Chair)

Moseley, Pope L.

Second Committee Member

Panganiban, Antonito

Third Committee Member

Timmins, Graham S.

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