SUMO-1 modification of centrosomal protein hNinein promotes hNinein nuclear localization.

A centrosomal-associated protein, ninein is a microtubules minus end capping, centrosome position, and anchoring protein, but the underlying structure and physiological functions are still unknown. To identify the molecules that regulate the function of human ninein in centrosome, we performed yeast two-hybrid screen and isolated the SUMO-conjugating E2 enzyme, Ubc9, and SUMOylation enhancing enzymes, including PIAS1 and PIASxalpha, as binding partners of hNinein. These interactions as well as the interaction between hNinein and SUMO-1 are also confirmed by a glutathione S-transferase (GST) pull-down experiment. Furthermore, the C-terminal region of hNinein can be SUMOylated in vitro and in HeLa cells transfected with a plasmid expressing GFP-hNinein. Our findings firstly place SUMOylation target on the centrosome structure protein, hNinein, which results in the switch localization from centrosome to nucleus, suggesting the importance of the SUMOylation of hNinein and probably other centrosomal proteins may also be involved in the centrosome activity.