INTERACTION OF P59(FYN) KINASE WITH THE DYNEIN LIGHT-CHAIN, TCTEX-1, AND COLOCALIZATION DURING CYTOKINESIS

The protein tyrosine kinase p59(fyn) (Fyn) plays important roles in bo th lymphocyte Ag receptor signaling and cytokinesis of proB cells, We utilized yeast two-hybrid cloning to identify the product of the tctex -1 gene as a protein that specifically interacts with Fyn, but not wit h other Src family kinases, Tctex-1 was recently identified as a compo nent of the dynein cytoskeletal motor complex. The capacity of a Tctex -1-glutathione S-transferase fusion protein to effectively bind Fyn fr om cell lysates confirmed the authenticity of this interaction. Tctex- 1 binding required the first 19 amino acids of Fyn and integrity of tw o lysine residues within this sequence that were previously shown to b e important for Fyn interactions with the immunoreceptor tyrosine-base d activation motifs (ITAMs) of lymphocyte Ag receptors, Expression of tctex-1 mRNA and protein was observed in all lymphoma lines analyzed, and immunofluorescence confocal microscopy localized the protein to th e perinuclear region. Analysis of a T cell hybridoma revealed prominen t colocalization of Tctex-1 and Fyn at the cleavage furrow and mitotic spindles in cells undergoing cytokinesis, Our results provide a uniqu e insight into a mechanism by which Tctex-1 might mediate specific rec ruitment of Fyn to the dynein complex in lymphocytes, which may be a c ritical event in mediating the previously defined role of Fyn in cytok inesis.