The. Sept1 By The Biological Significance And Sept12 Of The Biological Functions Regulated By Aurora B Phosphorylation

The septins are an evolutionarily conserved family of polymerizing GTP binding proteins originally discovered in budding yeast as a group of cell cycle mutants which cause defects in cytokinesis.It is now clear that septins are present in the fungi and animals,although apparently not in plants.In addition to their original role in cytokinesis,septins have been shown to have roles in coordinating nuclear division, membrane trafficking,organizing the cytoskeleton,apoptosis.In our previous study,we found that SEPT1 interact with Aurora B and is phosphorylated by Aurora B in vitro.In this study we found that SEPT1 colocalizated endogenously with Aurora B in the midbody during the cytokinesis of Jurkat T cell.Mass spectrum analysis revealed that SEPT1 was phosphorylated by Aurora B at T64 and S248 in vitro and further study showed that the two residues were also phosphorylate in vivo.In addition,our another study showed that SEPT1 was expressed specificly in haematopoietic system.,thus SEPT1 RNAi experiment in Jurkat cells indicated that SEPT1 was involved in the cytokinesis of Jurkat cells.We also found that the Aurora B phosphorylation of SEPT1 at Thr 64 and Ser 248 was associated with the cytokinesis of Jurkat cells.In addition,we reported the biochemical and immunocytochemical characterization of a recently identified mammalian septin,SEPT12,sharing closest homology to SEPT3 and SEPT9.SEPT12 can bind GTP in vitro and the mutation(Gly56 to Asn) in the GTP-bindng motif abrogated this binding.Immunocytochemical analysis revealed that the wild-type SEPT12 formed the filament structure and the SEPT12G56A appearared as large aggregates when transiently expressed in Hela cells. It was revealed that subcelluar localization of SEPT12 varied at interphase and mitotic phase.While SEPT12 formed filamentous structures at interphase,it was localized to the central spindle and to midbody during anaphase and cytokinesis,respectively.In addition,we found that SEPT12 can interact with SEPT6 and SEPT11 in vitro and in vivo.