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Abstract:
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The Aurora kinases are highly conserved serine /threonine kinases that play essential roles throughout mitosis . In metazoans , these functions are mediated by Aurora A and B at the spindle poles and the equatorial region respectively . I show here that Dictyostelium contains a single Aurora kinase , DdAurora that displays characteristics of both Aurora A and B . Like Aurora A , DdAurora has an extended N -terminal domain with an A -box and localizes to the spindle poles during early mitosis . Like Aurora B , DdAurora localizes to centromeres in metaphase , the central spindle during anaphase and the cleavage furrow at the end of cytokinesis . In addition to these known features of Aurora A and B , I found that DdAurora remains associated with centromeres during anaphase and telophase which has not been shown in any other organisms . INCENP is known to be an important binding partner of Aurora B . In Dictyostelium the conserved C -terminal IN -box domain of DdINCENP is essential for its interaction with DdAurora and for the localization of DdAurora to the central spindle . In contrast , the centromeric and spindle pole localization of DdAurora does not require an interaction with DdINCENP . Surprisingly , a truncated DdINCENP protein lacking the IN -box domain can still localize on centromeres and the central spindle even though it does not bind to DdAurora . I also found that the localization of DdAurora to the central spindle requires Kif12 , a protein similar to mitotic kinesin like protein 2 (MKLP2 ) . However , this requirement is suppressed by the overexpression of GFP -DdINCENP . GFP -DdINCENP can localize to the central spindle in the absence of Kif12 and it probably recruits DdAurora to the same location through their strong interaction . Finally , I demonstrated that Myosin II heavy chain is important for the proper localization of the DdAurora /DdINCENP complex to the cleavage furrow during late cytokinesis . With the exception of DdINCENP , no other binding partner or substrate of DdAurora has been identified in Dictyostelium . By performing large -scale immunoprecipitation in wild -type cells , I identified several potential binding partners /substrates of DdAurora , including topoisomerase B and HspA . Future esearch on these proteins may help to elucidate DdAurora function in different stages of M phase . |