Figure 2.

Loops form in transcribed G-rich DNAs. (A) Map of plasmid templates, which carry G-rich sequences downstream of a T7 promoter. (B) G-rich regions within the plasmid templates analyzed by EM. (C) Examples of loops formed upon transcription of pRX15F (Sμ repeat; left), pPH600 (Sγ3; middle), and pHumtel (telomeric repeat, right). DNA was transcribed in vitro, linearized with AflIII, and visualized by EM. Bar, 500 nm. (D) Maps of loops visualized in 15 randomly selected pRX15F (left), pPH600 (middle), and pHumtel (right) templates. Maps are drawn to scale.