Aurora A and B are required for the

Aurora A and B are required for the control of mitosis whereas Aurora C is mainly invoved in meiosis (Goldenson and Crispino, 2015). Interestingly, Aurora B is partnered with inner centromere protein (INCENP), survivin and Borealin to form a chromosomal passenger complex (CPC) that is critical for the kinetochore-microtubule attachment during cytokinesis (Terada, 2001, Vernos, 2004, Ruchaud et al., 2007, Vader et al., 2007). Functionally, Aurora B mainly acts at the transition from metaphase to the end of mitosis and regulates chromosomal condensation and segregation, spindle assembly checkpoint, and cytokinesis (Fu et al., 2007, Goldenson and Crispino, 2015). The expression downregulation or activity inhibition of Aurora B protein leads to failure in cytokinesis and formation of of polyploid Fmoc-L-Arg(Aloc)2-OH in Drosophila and vertebrates (Giet and Glover, 2001, Mathieu et al., 2013, Zekri et al., 2015). Aurora B functions in cell division through its phosphorylation on multiple substrates (Fu et al., 2007, Goldenson and Crispino, 2015). For example, Aurora B can phosphorylate histone H3 that is involved in chromatin condensation and separation during mitosis (Adams et al., 2001, Giet and Glover, 2001). Recent studyies in the fruit fly reported that Aurora B phosphorylates not only cyclin B to delay cytokinesis abscission in germ cells but also Lgl (Lethal giant larvae) protein to induce mitotic spindle orientation in epithelial cells (Mathieu et al., 2013, Bell et al., 2015). In addition, substrates for Aurora B also include centromere protein A (CENP-A), GTPase-activating protein MgcRacGAP, mitotic-centromere-associated kinesin (MCAK), histone 2A, survivin, nuclear distribution protein C (NudC), microtubule-binding protein Hec1, and Ataxin-10 (Zeitlin et al., 2001, Minoshima et al., 2003, Knowlton et al., 2006, Delacour-Larose et al., 2007, Zhu et al., 2013, Tian et al., 2015, Weiderhold et al., 2016). To date, Aurora B kinase has not been well characterized in the silkworm, Bombyx mori. The role of silkworm Aurora B kinase (referred to hereafter as BmAurB) has been preliminarily examined (Mon et al., 2014). In this study, we cloned the full-length cDNA of silkworm Aurora B kinase gene (referred to hereafter as BmAurB) and analyzed its phylogenetic relationship with Aurora kinases from other species. The spatio-temporal expression of the BmAurB gene during silkworm larval development was also profiled. We finally investigated the roles of BmAurB kinase in silkworm cells by RNA interference (RNAi) or inhibitor treatment.
Materials and methods
Result
Discussion Aurora kinases belong to the serine/threonine kinases and are involved in cell cycle control and mitosis (Katayama et al., 2003, Fu et al., 2007, Goldenson and Crispino, 2015). To date, there are three Aurora kinase family members (A, B and C) to have been identified in metazoan. Interestingly, Aurora B kinase is highly expressed during G2/M transition and has been demonstrated as a part of the CPC that is required for the kinetochore-microtubule attachments during cytokinesis (Vader et al., 2007, Goldenson and Crispino, 2015). In this study, we aimed to characterize cDNA sequence, expression and function of Aurora B in the silkworm. Firstly, we cloned full-length cDNA sequence of silkworm Aurora B gene (BmAurB). Sequence analysis found that the predicted BmAurB protein sequence contains a catalytic S_TKc domain and the S_TKc domain of the BmAurB kinase shared a high sequence similarity with Aurora B kinases from mammalian and insects, indicating a functional conservation of the BmAurB kinase. Notably, the results of phylogenetic analysis between BmAurB and other Aurora kinases, together with the fact that the types of the Aurora kinases vary in metazoan (Goldenson and Crispino, 2015), suggesting that the separation of Aurora kinases may have occurred after separation between mammalian and insect, and prior to radiation of either mammalian or insects.