The involvement of protein synthesis elongation factor 1 alpha in the organization of microtubules on the perinuclear region during the cell cycle transition from M phase to G(1) phase in tobacco BY-2 cells

Association of the organization of microtubules (MTs) in the perinuclear region with a 49-kDa protein, that is immunologically cross-reactive to a 51-kDa protein isolated from sea urchin centrosomes and has been shown to play some roles in the organization of MTs in animal cells (Toriyama et al.: Cell Motil. Cytoskeleton 9, 117-128, 1988), was examined during the cell cycle transition from M phase to G(1) phase using the highly synchronized tobacco BY-2 cells under confocal laser scanning microscopy (CLSM). After double staining with an antibody against the 51-kDa protein and with an antibody against tubulin, it was revealed that the 49-kDa protein was closely associated with the organization of MTs on the perinuclear regions during this stage under the CLSM. Notably, microfilaments (MFs) were not associated with the organization of MTs in the perinuclear region. This observation suggests that the 49-kDa protein plays a specific role in the organization of MTs on the perinuclear regions during the cell cycle transition from M phase to G(1) phase. To understand the molecular characteristics of the 49-kDa protein further, the search for cDNA encoding the 49-kDa protein was conducted in a cDNA expression library prepared from rapidly growing tobacco BY-2 cells using monoclonal antibodies against the 51-kDa protein. Determination of the base sequence of the isolated clone revealed that it encodes protein synthesis elongation factor (EF)-1 alpha. Thus the significance of the involvement of the 49-kDa protein as EF-1 alpha in the organization of MTs on the perinuclear regions is discussed in relation to other cellular functions.