Final Activity Report Summary - SPINDLE ASSEMBLY (Keeping the spindle in shape: identification and characterization of new components involved for spindle formation)
The bipolar spindle is a macromolecular machine used by the cell during mitosis to achieve proper chromosome segregation and division. Bipolarity is essential for proper distribution of the genetic material. In order to identify factors controlling bipolarity we used in vitro formed spindle-like structures in meiotic Xenopus egg extract after the addition of the small GTPase Ran. GTP-bound Ran appears to affect multiple aspects of microtubule behaviour, including the induction of bipolar spindle-like microtubule assemblies and we used this system to identify Ran effectors involved in spindle bi-orientation.
We identified a complex that is required for the conversion of aster-like to spindle-like structures in Xenopus egg extract consisting of five proteins: two characterised MAPs (TPX2, XMAP215), a plus end-directed motor, Eg5, a mitotic kinase, Aurora A, and HURP, a protein associated with hepatocellular carcinoma. HURP protein was further characterized and found to be a new and essential component of the mitotic apparatus not only in vitro but also in mammalian cells. HURP is required in mammalian cells for proper spindle formation correct entry into anaphase and segregation of the chromosomes.
HURP is the first MAP identified so far to affect microtubule stability and organisation in vitro by inducing a novel conformation of tubulin. HURP may exert its potential oncogenic action on hepatocellular carcinoma through its effect on tubulin conformation and stability.
We identified a complex that is required for the conversion of aster-like to spindle-like structures in Xenopus egg extract consisting of five proteins: two characterised MAPs (TPX2, XMAP215), a plus end-directed motor, Eg5, a mitotic kinase, Aurora A, and HURP, a protein associated with hepatocellular carcinoma. HURP protein was further characterized and found to be a new and essential component of the mitotic apparatus not only in vitro but also in mammalian cells. HURP is required in mammalian cells for proper spindle formation correct entry into anaphase and segregation of the chromosomes.
HURP is the first MAP identified so far to affect microtubule stability and organisation in vitro by inducing a novel conformation of tubulin. HURP may exert its potential oncogenic action on hepatocellular carcinoma through its effect on tubulin conformation and stability.