The murine Gcap14 gene encodes a novel microtubule binding and bundling protein

Characterization of human Ccser2 as a protein tracking the plus-ends of microtubules

OBJECTIVE

Microtubules, which are closely related to cell proliferation, have been the promising therapeutic target of cancer. Therefore, it is necessary to understand the intracellular control mechanisms of microtubules, the whole picture of which is still unclear though. Intracellular dynamics of microtubules are regulated by various microtubule-associated proteins, one group of which is microtubule plus-end-tracking proteins (+ TIPs), localizing to the extending tips of microtubules. Here, we report the identification and analysis of Ccser2 as a new + TIP in human breast cancer MCF-7 cells.

RESULTS

Ccser2 was found to be a member of + TIPs by microscopic observations including time-lapse imaging. The C-terminal region of Ccser2, including two SxIP motifs, was likely to be important for the tracking function. In MCF-7 cells, endogenous Ccser2 was mainly detected in the peripheral regions of microtubule fibers, suggesting that Ccser2 functions in cell projections.

Lyar, a cell growth-regulating zinc finger protein, was identified to be associated with cytoplasmic ribosomes in male germ and cancer cells

Translational control is a basic mechanism for gene regulation in cells and important for tissue growth and development in mammals. Deregulation of the mechanism thus causes diseases such as cancer. Considering the importance of the ribosome as a factory of polypeptide synthesis, some new factors have been expected to be associated with the ribosome and involved in translational control. Our proteomic survey for these factors identified a zinc finger protein, Lyar, in cytoplasmic ribosomes of the rodent testis. Subcellular fractionation of the testis provided data supporting association of Lyar with ribosomes. Lyar was then suggested to be included in the 60S large subunit, but not in polysomes, by ultracentrifugation of testicular ribosomes. While analysis of tissue distribution of Lyar has indicated its testis-predominant expression, Lyar mRNA was expressed in the cancer cells originated from tissues other than testis, and Lyar promoted proliferation of NIH-3T3 cells. Furthermore, translation was increased by Lyar in vitro, pointing out the first experimental link between this protein and translation. Taken together, Lyar seems to be a new player in translational control and a potential target for cancer therapy.