Regulator Of Centriole Biogenesis Research Articles

A role for Cep70 in centriole amplification in multiciliated cells

Centriole amplification in multiciliated cells occurs in a pseudo-cell cycle regulated process that typically utilizes a poorly characterized molecularly dense structure called the deuterosome. We identified the centrosomal protein Cep70 as a novel deuterosome-associated protein that forms a complex with other deuterosome proteins, CCDC78 and Deup1. Cep70 dynamically associates with deuterosomes during centriole amplification in the ciliated epithelia of Xenopus embryos. Cep70 is not found in nascent deuterosomes prior to amplification. However, it becomes localized at deuterosomes at the onset of centriole biogenesis and remains there after the completion of centriole amplification. Deuterosome localization requires a conserved C-terminal “Cep70” motif. Depletion of Cep70 using morpholino oligos or CRISPR/Cas9 editing in F0 embryos leads to a severe decrease in centriole formation in both endogenous MCCs, as well as ectopically induced MCCs. Consistent with a decrease in centrioles, endogenous MCCs have defects in the process of radial intercalation. We propose that Cep70 represents a novel regulator of centriole biogenesis in MCCs.

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

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.