Fig. 5: RRN3 binding to human Pol I.
a, RRN3 (maroon, cartoon representation) binds the Pol I (gray, surface representation) at stalk and RPA1 dock regions. Disordered parts of the human RRN3 that harbor phosphorylation sites are shown with maroon dotted lines (not to scale). Phosphorylation sites are marked with circles: activating phosphorylation sites in green21,22, inactivating phosphorylation sites in cyan20,21,58, and a phosphorylation site with an unknown role in yellow59. The position of the RPA49 tWH domain from the Pol I EC is encircled and filled with transparent purple. N and C termini are labeled. b, RPA43 subunit and RRN3 are shown in cartoon representation, and the rest of Pol I is shown in surface representation, colored according to the subunit as in Fig. 1. The upper part of the RPA43 subunit from the Pol I–RRN3 structure (light blue) swings away (black arrow) from RRN3, compared with the RPA43 subunit, from the Pol I EC structure (dark blue, transparent). The lower part remains anchored to the core. The closest contact point between RPA43 and RRN3 (close-up view) is the location of the two residues (S199 and T200), which can carry an inactivating phosphorylation (cyan circle). The local resolution does not allow us to unambiguously identify the contacting residues from RPA43. RPA43 from the Pol I EC complex (dark blue transparent) would clash with the RRN3, and thus it swings by 5 Å away (white arrow) into the Pol I–RRN3 conformation.
