The following information accompanied stocks donated to the Bloomington Stock Center by Dirk Beuchle and Beat Suter, University of Bern. Top3betaY332F is a CRISPR-induced mutation introducing a Y332F substitution into the Top3beta protein to eliminate a tyrosine important for catalytic activity. Top3betaDeltaRGG is a CRISPR-induced mutation deleting RGG boxes important for RNA and protein binding from the Top3beta protein. These mutations were generated by Shohreh Teimuri.