Fig. 2. (A) Luciferase activity in transiently transfected L929 control and mtDNA-depleted cells with luciferase constructs driven by c-myc, c-Jun, authentic MMCP-6, c-fos and α-inhibin promoters. L929 (black) and mtDNA-depleted L929 (hatched) cells, were transiently co-transfected with β-galactosidase and the luciferase constructs. (B) CREB-dependent luciferase activity in L929, mtDNA-depleted L929, wild-type (wt) MERRF cybrid, mutated (mut) MERRF cybrid, 143B and ρ0 143B cells transiently transfected with the luciferase reporter construct driven by the α-inhibin promoter and an expression plasmid encoding β-galactosidase. (C) CREB-dependent luciferase activity in L929 (black) and mtDNA-depleted L929 (hatched) cells transiently transfected with K-CREB or M1-CREB, together with the CREB-sensitive luciferase reporter construct and an expression plasmid encoding β-galactosidase. Luciferase activity was determined 24 h post-transfection. Results are expressed in relative light units (RLU) after normalization for β-galactosidase activity (A) or in fold increase of control cells (B and D) as means ± 1 SD (*** and ###, significantly different from L929 and mtDNA-depleted L929 cells with P <0.001). (D) Western blot analysis of phospho-CREB (p-CREB) and CREB assessed for the different cell lines used in (B). (E) Western blot analysis for c-fos and α-tubulin assessed for L929 (lane 2) and mtDNA-depleted L929 (lane 1).