Figure 7.

C3 transferase represses MyoD promoter activity. MyoD promoter (DRR and PRR regions driving βgal reporter gene, Tapscott et al., 1992) was stably transfected in mouse C2 myoblasts and mouse 10T1/2 fibroblasts in the presence of PSV2neo encoding a gene for resistance to geneticin (G418). After selection with G418, a pool of clones was cultured as a permanent cell line. (A) Shown is βgal activity in myoblasts (Myob.), in fibroblasts (Fibr.), and after the onset of differentiation (Myot.). βgal values are expressed relative to that of myoblasts set as 100%. (B) To determine the effect of C3 transferase on MyoD promoter activity, cells stably transfected with MyoD promoter were grown for 48 h in proliferation medium and then treated for 24 h with 4 μg/ml C3 transferase. As a control, CMVβgal was transiently transfected in myoblasts cells in the presence or not of C3 transferase. βgal values determined in nontreated cells were fixed at 100 for each case, and those obtained after C3 treatment were expressed relative to their respective control.