Fig. 4.

Transcription inhibition with actinomycin D (ActD) or DRB in TnFL/DsRed or TnCT/DsRed transiently transfected C2C12 cells. a Incubating transfected cells in 0.05 μg/ml ActD for 3 h did not seem to affect fibrillarin distribution, yet TnFL/DsRed was dispersed into the nucleoplasm. In contrast, TnCT/DsRed remained punctate and co-localized with some fibrillarin puncta. Notably, the weak diffusive distribution of TnCT/DsRed in the nucleoplasm disappeared. b When only RNA Pol II was inhibited with 25 μg/ml DRB for 3 h, fibrillarin adopted a large punctate pattern in both TnFL/DsRed- and TnCT/DsRed-transfected cells. In contrast, TnCT/DsRed showed a diffuse nucleoplasmic distribution while TnFL/DsRed remained mainly punctate. c RNA Pol I and Pol II inhibition by 20 μg/ml ActD for 3 h resulted in diffuse fibrillarin dispersion into the nucleoplasm. Consistently, both TnFL/DsRed and TnCT/DsRed showed mainly a diffuse nuclear distribution pattern. Data are representative of two independent experiments, and at least 50 cells were analyzed per group. Scale bars, 25 μm