The ubiquitin proteasome system is essential for maintaining nuclear and cytoplasmic protein levels. Currently, the Boyd lab is investigating the role that ubiquitin and proteasome play during a cellular stress response. Our studies have shown that cellular stress causes the re-localization of ubiquitin and proteasome into distinct spheres within the nuclei of both oocytes and embryos. Different stressors, such as high salt exposure, oxidative stress, and starvation induce these ubiquitin- and proteasome-rich nuclear spheres. The function of the nuclear spheres is currently unknown. Embryos possessing nuclear spheres fail to hatch. This evidence suggests that the presence of nuclear spheres correlates with embryonic lethality. Proteasome inhibitor experiments have shown that without proteasome activity these nuclear spheres do not form during cellular stress. Antibody staining of temperature sensitive
uba-1 worm strains have shown that ubiquitination is required for nuclear sphere formation. Live cell imagining of ubiquitin and proteasome has shown that during stress both ubiquitin and proteasome co-localize and that ubiquitin arrives before proteasome. This evidence suggests that a proteolytic event is needed to form the nuclear spheres. Recent work in the Boyd lab has been focused on elucidating the pathway leading to nuclear sphere formation. The overall results indicate that both ubiquitin and proteasome play a fundamental role in cellular stress, and that this event may be occurring inside the nucleus. We aim to elucidate the pathway of how ubiquitin and the 26 S proteasome affect nuclear sphere formation during stress conditions. .