Figure 1

Large TRF2 complex formation on DNA involves protein stacking leading to greater complex heights.

(a) Schematic representations of the domain structure of TRF2 (left) and T270 DNA substrate (right). B: the basic domain. M: the Myb type domain. T270 DNA contains two (TTAGGG)₁₃₅ regions (purple) separated by a short linker region (23 bp, black) and flanking non-telomeric regions (blue). (b,c) AFM images of T270 bound by multiple small complexes (white arrows, volume < 500 nm³) with a contour length of 1702.0 nm (b) and a higher order oligomeric TRF2 complex (the white arrow, 1841 nm³) with a DNA contour length of 1457.5 nm (c). The AFM images in (b,c) are 0.5 μm × 0.5 μm. (d,e) AFM volume (top) and height (bottom) distributions of small (d, N = 134) and large TRF2 complexes (e, N = 69). The red lines are Gaussian fits to the data. The volumes of small complexes displayed two distinct peaks at 142.3 ± 93.9 nm³ and 266.6 ± 53.4 nm³ (R² = 0.92), while their heights displayed a single peak at 0.5 ± 0.4 nm (R² = 0.91). The heights of large complexes displayed two distinct peaks at 1.3 ± 0.8 and 2.4 ± 0.4 nm (R² = 0.81). Note that the AFM volume distribution of TRF2 dimers on DNA is broader than protein alone (Supplementary Fig. 1c).