Figure 6. Binding specificities of TFAM to G4 DNA.

(a) Examples of complexes obtained upon incubation of the indicated amounts of TFAM (in μM) with G4 tetramers of various lengths and sequences. (−) indicates absence of protein; (U), unfolded oligonucleotide. The gel on the left panel contains 0.5 μM G4-DNA/lane, the others contain 0.2 μM. (b) TFAM/G4 complexes obtained with tetramolecular G4 (0.2 μM) assembled from LSP sequence containing a tract of four (G4) and five (G5) guanines. (c) Complexes obtained between TFAM and bimolecular G4-DNAs formed by G₄T₄G₄, G₄T₄G₄TGACT and TCAG₄T₄G₄TGACT oligonucleotides. The topologies of the bimolecular substrates are schematized above each gel, with folding involving diagonal loops here, although lateral loops can also exist. (−) indicates absence of protein. U: unfolded oligonucleotide. Each lane contains 0.8 μM of the DNA substrates (0.4 μM dimers). Lanes (2–4), (6–8) and (10–12) contain 0.5, 1 and 2 μM of TFAM, respectively. Asterisks for TCAG₄T₄G₄TGACT indicate other G4 species such as parallel tetramers.