Bluetongue virus infection induces aberrant mitosis in mammalian cells
1 The Pirbright Institute, Pirbright, Woking GU24 0NF, UK
2 Section of Oncology and Clinical Research, Leeds Institute of Cancer and Pathology, Leeds University, Leeds LS9 7TF, UK
3 Section of Ophthalmology and Neuroscience, Leeds Institute of Biomedical and Clinical Sciences, Leeds University, Leeds LS9 7TF, UK
4 School of Pharmacy, University of London, London WC1N 1AX, UK
5 Faculty of Pharmacy, Istanbul Kemerburgaz University, Bagcilar, Istanbul, Turkey
6 Australian Animal Health Laboratory, Geelong VIC 3220, Australia
7 Current address: MRC-University of Glasgow Centre for Virus Research, 464 Bearsden Road, Glasgow G61 1QH, UK
Virology Journal 2013, 10:319 doi:10.1186/1743-422X-10-319Published: 28 October 2013
Bluetongue virus (BTV) is an arbovirus that is responsible for ‘bluetongue’, an economically important disease of livestock. Although BTV is well characterised at the protein level, less is known regarding its interaction with host cells. During studies of virus inclusion body formation we observed what appeared to be a large proportion of cells in mitosis. Although the modulation of the cell cycle is well established for many viruses, this was a novel observation for BTV. We therefore undertook a study to reveal in more depth the impact of BTV upon cell division.
We used a confocal microscopy approach to investigate the localisation of BTV proteins in a cellular context with their respective position relative to cellular proteins. In addition, to quantitatively assess the frequency of aberrant mitosis induction by the viral non-structural protein (NS) 2 we utilised live cell imaging to monitor HeLa-mCherry tubulin cells transfected with a plasmid expressing NS2.
Our data showed that these ‘aberrant mitoses’ can be induced in multiple cell types and by different strains of BTV. Further study confirmed multiplication of the centrosomes, each resulting in a separate mitotic spindle during mitosis. Interestingly, the BTV NS1 protein was strongly localised to the centrosomal regions. In a separate, yet related observation, the BTV NS2 protein was co-localised with the condensed chromosomes to a region suggestive of the kinetochore. Live cell imaging revealed that expression of an EGFP-NS2 fusion protein in HeLa-mCherry tubulin cells also results in mitotic defects.
We hypothesise that NS2 is a microtubule cargo protein that may inadvertently disrupt the interaction of microtubule tips with the kinetochores during mitosis. Furthermore, the BTV NS1 protein was distinctly localised to a region encompassing the centrosome and may therefore be, at least in part, responsible for the disruption of the centrosome as observed in BTV infected mammalian cells.