Function and localization of nuclear UPS components. Function and localization of nuclear UPS components. Micrographs on the right show confocal immunofluorescence of HEp-2 cells with antibodies against components of the UPS: rabbit polyclonal anti-ubiquitin (Ub FL-76; red), mouse monoclonal anti-20S proteasome core subunits (20S core; gray), mouse monoclonal anti-19S regulator (19S Rpt6, purple) and rabbit anti-ubiquitin-conjugating enzyme E2 (UbcH6, green). Micrographs in the left show corresponding differential interference contrast (DIC) images. Ub, ubiquitin; 19S-20S-19S, 26S proteasome; 19S, 19S regulator complex; E1, ubiquitin-activating enzyme; E2, ubiquitin-conjugating enzyme; E3, ubiquitin ligase. Bar, 5 μm. Anna von Mikecz J Cell Sci 2006;119:1977-1984 © The Company of Biologists Limited 2006