Fig. 3. Mitochondrial transcription factor A (mtTFA) is enriched in punctate DNA-positive structures. Primary skin fibroblasts, HeLa cells and 143B cells were decorated with antibodies against DNA and mitochondrial transcription factor A (mtTFA) and analyzed by conventional (Fibroblasts) or confocal (HeLa, 143B) fluorescence microscopy. The insets are enlargments of the boxed image regions. In fibroblasts, mtTFA is restricted to punctate mtDNA-positive structures. In Hela and 143B cells, mtTFA has a more homogeneous intramitochondrial distribution and is partially enriched in some mtDNA-positive structures. Bars, 10 µm.