(a) 10R UV crosslinked to U87 nuclear extract (NE) and digested with RNAse A (0.5 ug) (lane 3), RNAse T1 (10U) (lane 4), both (0.5ug RNAse A/10U RNAse T1) (lane 5), or nothing (lane 2), and separated by 10% SDS-PAGE. (b) 0.1 pmoles of 10R in water (lanes 1, 2 and 4) or 200 mM KCl and 500 μM pyridostatin (PDS) (lanes 3 and 5), IPed with BG4 antibody (lanes 4 and 5) or beads alone (lanes 2 and 3). Products were separated by 10% SDS-PAGE (top) and by 8M Urea/10% PAGE (bottom). (c) Representative G-Q folding conformations of 10 repeats of GGGGCC RNA. Numbers indicate G-tracts that participate in GQs or linear fragments. The right most conformation represents 8 consecutive G-tracts forming an octamer. Beneath, a depiction of one quartet, with the N7 (replaced with C in 7-deaza GTP) position surrounded by red dashed oval (d) 10R (lanes 1 and 3) and 10R-7dG (lanes 2 and 4) heated to 95°C (lanes 3 and 4) or left on ice (lanes 1 and 2), crosslinked to NE, digested with RNAse A/T1 (.5 ug/10U) and separated by 10% SDS-PAGE. (e) 10R-G (lanes 1, 3, 5 and 7) and 10R-G7dG (lanes 2, 4, 6 and 8) heated to 95°C in water (lanes 5 and 6) or 100 mM KCl (lanes 7 and 8) or left on ice (lanes 3 and 4), crosslinked to NE, digested with RNAse A/T1 (0.5 μg/10 U) and separated by 10% SDS-PAGE. This gel was cropped to remove two intervening lanes between lanes 6 and 7.