Abstract 5354: HPV-16 E7 oncoprotein induces centriole multiplication through deregulation of PLK4, a master regulator of centriole biogenesis

Abstract

Abstract Human papillomavirus (HPV)-associated neoplasms exhibit abnormal centrosome and centriole numbers that can cause mitotic defects, chromosome missegregation and aneuploidy. Centrosomes are the major microtubule-organizing centers in most mammalian cells and orchestrate the formation of mitotic spindle poles. The centrosome consists of a pair of centrioles that normally duplicate precisely once prior to mitosis. The HPV-16 E7 oncoprotein has been found to rapidly stimulate centriole overduplication within a single cell division cycle, thereby increasing the risk for cell division errors. We discovered that this activity of the HPV-16 E7 oncoprotein involves the concurrent formation of multiple daughter centrioles at single maternal centrioles (centriole multiplication). We found that deregulated cyclin E/cyclin dependent kinase 2 (CDK2) activity, as occurs following HPV-16 E7 oncoprotein expression, leads to the aberrant recruitment of polo-like kinase 4 (PLK4) to maternal centrioles, which is subsequently degraded by the SCF ubiqutin ligase complex. These and several other results underscore that the level of PLK4 at maternal centrioles is rate-limiting for centriole multiplication. Hence, we asked whether the HPV-16 E7 oncoprotein can alter PLK4 expression and/or localization. We found aberrant PLK4 protein expression at maternal centrioles in primary human keratinocytes engineered to stably express HPV-16 E7. Real-time quantitative RT-PCR revealed an increase in PLK4 transcription in keratinocytes stably expressing HPV-16 E7. The ability of HPV-16 E7 to upregulate PLK4 mRNA was found to depend on its ability to degrade the retinoblastoma (pRb) protein, suggesting a role of E2F-mediated gene transcription in deregulation of PLK4. Collectively, these results highlight the critical role of PLK4 as a regulator of centriole biogenesis and identify PLK4 as a novel target for small molecules to prevent centriole abnormalities, mitotic infidelity and malignant progression in HPV-associated neoplasms. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5354.