SIAH-1 interacts with α-tubulin and degrades the kinesin Kid by the proteasome pathway during mitosis

SIAH-1, a human homologue of the Drosophila seven in absentia (Sina), has been implicated in ubiquitin-mediated proteolysis of different target proteins through its N-terminal RING finger domain, SIAH-1 is also induced during p53-mediated apoptosis, Furthermore, SIAH-1-transfected breast cancer cell line MCF-7 exhibits an altered mitotic process resulting in multi-nucleated giant cells, Now, using the two-hybrid system, we identified two new SIAH interacting proteins: Kid (kinesin like DNA binding protein) and a-tubulin. We demonstrate that SIAH is involved in the degradation of Kid via the ubiquitin-proteasome pathway. Our results suggest that SIAH-1 but not its N-terminal deletion mutant, affects the mitosis by an enhanced reduction of kinesin levels, Our results imply, for the first time, SIAH-1 in regulating the degradation of proteins directly implicated in the mitotic process.