| Guanine nucleotide exchange factor , Tiam 1 , directly binds to c Myc and interferes with c Myc mediated apoptosis in rat 1 fibroblasts . ^^^ We report in the present study on another protein , Tiam 1 , which is a specific guanine nucleotide exchange factor of Rac 1 and which binds to c Myc and modulates several of its biological functions . ^^^ We were able to detect the direct binding and in vivo association between c Myc and Tiam 1 . ^^^ Overexpression of Tiam 1 repressed the luciferase activity of c Myc and also inhibited the c Myc apoptotic activity through this protein protein interaction . ^^^ Taken together , we concluded that Tiam 1 is another c Myc regulator , working in the nuclei to control c Myc related apoptosis . . ^^^ |