Fbw7−/− cells, +/− MG132, were transfected with PGC-1α, Fbw7α, Fbw7β, Fbw7α mutants and HA-ubiquitin, as noted. 18h later, cells were lysed, aliquots were Western blotted with anti-HA (panel A, B) to detect total cellular ubiquitin-protein conjugates or with anti-PGC-1α (panel C, D) to detect total cellular PGC-1α. Additional aliquots were immunoprecipitated with anti-HA and thereafter Western blotted for PGC-1α (panel E) to determine specific ubiquitin-PGC-1α conjugates. Ubiquitin-PGC-1α conjugates are marked by bracket. Low molecular weight conjugates are seen below ~225 kDa.