Characterization of Npa3 GTPase domain mutants. Npa3-degron cells were transformed with a yeast centromeric plasmid (pRS415) carrying Npa3-FLAG (Npa3 WT), Npa3-FLAG D106A, or Npa3-FLAG Q110L under the control of its natural promoter and terminator. A, serial dilutions of cells grown in liquid cultures at 25 °C overnight were spotted on plates containing 10 μm CuSO4 and grown for 3 days at 25 °C (no Npa3-degron depletion) or spotted on plates with no added CuSO4 and grown for 2 days at 37 °C (Npa3-degron depletion induced). B, Rpb1 localization in cells grown for 6 h at 37 °C (Npa3-degron depletion induced) assessed by immunofluorescence, using a 4H8 anti-Rpb1 antibody.