[show abstract][hide abstract] ABSTRACT: We previously observed that high-risk human papillomavirus type 16 (HPV16) E7 expression leads to the delocalization of dynein from mitotic spindles (C. L. Nguyen, M. E. McLaughlin-Drubin, and K. Munger, Cancer Res. 68:8715-8722, 2008). Here, we show that HPV16 E7 associates with nuclear mitotic apparatus protein 1 (NuMA) and that NuMA binding and the ability to induce dynein delocalization map to similar carboxyl-terminal sequences of E7. Additionally, we show that the delocalization of dynein from mitotic spindles by HPV16 E7 and the interaction between HPV16 E7 and NuMA correlate with the induction of defects in chromosome alignment during prometaphase even in cells with normal centrosome numbers. Furthermore, low-risk HPV6b and HPV11 E7s also associate with NuMA and also induce a similar mitotic defect. It is possible that the disruption of mitotic events by HPV E7, via targeting of the NuMA/dynein complex and potentially other NuMA-containing complexes, contributes to viral maintenance and propagation potentially through abrogating the differentiation program of the infected epithelium. Furthermore, in concert with activities specific to high-risk HPV E6 and E7, such as the inactivation of the p53 and pRB tumor suppressors, respectively, the disruption of the NuMA/dynein network may result in mitotic errors that would make an infected cell more prone to the accumulation of aneuploidy even in the absence of supernumerary centrosomes.
Journal of Virology 01/2009; 83(4):1700-7. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dynein is a minus end-directed microtubule motor that transports numerous cargoes throughout the cell. During mitosis, dynein motor activity is necessary for the positioning of spindle microtubules and has also been implicated in inactivating the spindle assembly checkpoint. Mutations in dynein motor and/or accessory proteins are associated with human disease, including cancer, and the delocalization of dynein from mitotic spindles has been correlated with an increased incidence of multipolar spindle formation in some cancer cells that contain supernumerary centrosomes. The high-risk human papillomavirus type 16 (HPV16) E7 oncoprotein induces centrosome overduplication and has been shown to cause multipolar mitotic spindle formation, a diagnostic hallmark of HPV-associated neoplasias. Here, we show that HPV16 E7 expression leads to an increased population of mitotic cells with dynein delocalized from the mitotic spindle. This function maps to sequences of HPV16 E7 that are distinct from the region necessary for centrosome overduplication. However, contrary to previous reports, we provide evidence that dynein delocalization by HPV16 E7 is neither necessary nor sufficient to cause the formation of multipolar mitoses.
Cancer Research 12/2008; 68(21):8715-22. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: The human papillomavirus (HPV) E7 oncoprotein has been shown to associate with cyclin/CDK2 complexes. Here we present evidence that HPV E7 proteins can associate with cyclin A/CDK2 and cyclin E/CDK2 complexes in cells that lack retinoblastoma tumor suppressor family members through sequences outside of the core retinoblastoma tumor suppressor binding site. Moreover, we show that HPV16 E7 can directly associate with cyclin A/CDK2 and cyclin E/CDK2 complexes. These results suggest that cyclin/CDK2 complexes may be components of HPV E7-associated cellular complexes that do not contain retinoblastoma tumor suppressor family members.
[show abstract][hide abstract] ABSTRACT: Expression of a high-risk human papillomavirus (HPV) E7 oncoprotein is sufficient to induce aberrant centrosome duplication in primary human cells. The resulting centrosome-associated mitotic abnormalities have been linked to the development of aneuploidy. HPV type 16 (HPV16) E7 induces supernumerary centrosomes through a mechanism that is at least in part independent of the inactivation of the retinoblastoma tumor suppressor pRb and is dependent on cyclin-dependent kinase 2 activity. Here, we show that HPV16 E7 can concentrate around mitotic spindle poles and that a small pool of HPV16 E7 is associated with centrosome fractions isolated by sucrose density gradient centrifugation. The targeting of HPV16 E7 to the centrosome, however, was not sufficient for centrosome overduplication. Nonetheless, we found that HPV16 E7 can associate with the centrosomal regulator gamma-tubulin and that the recruitment of gamma-tubulin to the centrosome is altered in HPV16 E7-expressing cells. Since the association of HPV16 E7 with gamma-tubulin is independent of pRb, p107, and p130, our results suggest that the association with gamma-tubulin contributes to the pRb/p107/p130-independent ability of HPV16 E7 to subvert centrosome homeostasis.
Journal of Virology 01/2008; 81(24):13533-43. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Oncogenes encoded by human tumor viruses play integral roles in the viral conquest of the host cell by subverting crucial and relatively non-redundant regulatory circuits that regulate cellular proliferation, differentiation, apoptosis and life span. Human tumor virus oncoproteins can also disrupt pathways that are necessary for the maintenance of the integrity of host cellular genome. Some viral oncoproteins act as powerful mutator genes and their expression dramatically increases the incidence of host cell mutations with every round of cell division. Others subvert cellular safeguard mechanisms intended to eliminate cells that have acquired abnormalities that interfere with normal cell division. Viruses that encode such activities can contribute to initiation as well as progression of human cancers.
[show abstract][hide abstract] ABSTRACT: Papillomaviruses are small nonenveloped viruses with 55- nm-diameter icosahedral capsids that contain double-stranded DNA genomes of approximately 8,000 bp. They are widely distributed throughout the animal kingdom, specifically infect squamous epithelia, and cause the generation of warts. An infectious etiology of warts was long suspected and eventually proven in the 19th century. One of the first recorded experi- mental wart transmission cases in humans appears to have been accidental and was reported in 1845 by a certain Chan- dler, who "when removing a large acicular condyloma with his instrument injured his assistance beneath the thumbnail. On the injured place there appeared after a short time a wart, which was repeatedly destroyed, but reappeared, until the nail of the injured thumb was removed" (cited in reference 134). Ullmann also noted a similar accidental transmission of laryn- geal papillomas and performed self-inoculation experiments with laryngeal papilloma extracts applied to scarified sites on his forearm, and these experiments yielded warts after a lengthy latency period of 9 months (134). Similar inoculation experiments had also been performed with extracts derived from common hand warts (23), and serial inoculation experi- ments with human subjects were performed (78). Genital warts and cervical cancer were long regarded as manifestations of then-common venereal diseases such as syphilis and gonorrhea (75). This theory was contested in a rather ghastly paper published in 1917. Extracts of a penile condyloma that was harvested from a young medical student who did not exhibit other overt symptoms of venereal diseases were used to inoculate sites on the forearms of the author and his assistant as well as the genital mucosa of a "virgo intacta." After a period of 2.5 months, the unfortunate female subject developed genital condyloma, and flat warts appeared on the forearms of two male probands (139). These and other exper- iments led to the realization that genital warts represent dis- tinct disease entities that are caused by a transmissible agent. The concept that some warts have an inherent propensity for malignant progression was established from studies by Shope, Rous, and others who studied experimental transmission of warts that occur naturally in cottontail rabbits. These investi- gators discovered that lesions that formed in domestic rabbits after inoculation with cottontail rabbit wart extracts were par- ticularly susceptible to malignant progression (116). Careful transmission studies demonstrated that such extracts caused the emergence of warts only in rabbits and not in other ani- mals, thus illustrating the exquisite species specificity of pap- illomaviruses (117). Harald zur Hausen's laboratory was the first to demonstrate that genital warts contain human papillomavirus (HPV) ge- nomes (28, 53). Subsequent low-stringency hybridization ex- periments with HPV sequences isolated from genital warts performed in his laboratory led to the discovery of related HPV sequences in cervical cancer tissues (38).
Journal of Virology 12/2004; 78(21):11451-60. · 5.08 Impact Factor