Figure 5.

Low-temperature and corr-4a effects on the ubiquitin–proteasome system. HeLa cells were transfected with luciferase (FL-luc), a luciferase construct with a degron sequence added (CL-1), a luciferase construct with four in-frame ubiquitin sequences at the N terminus (4-ub), or with a luciferase construct containing a C-terminal sequence of p21 that targets proteins to the proteasome without ubiquitin modification (see Table 1). Luciferase activity for each construct was normalized to light units measured in control (untreated) cells cultured at 37°C (onefold). The increases in luciferase activity are fold increases (n = 3; *P < 0.05; **P < 0.01; ***P < 0.001).