FANCD2 and Friedreich ataxia: Similarly, to our observation in ∆Np63 depleted A431 cells (Fig. S5C), sh-USP28 or AZ1 treated cells failed to increase FANCD2 protein abundance upon 6 h post-CPPD (Fig. S6B), implying a connection between USP28-∆Np63 and the FA pathway in SCC cells.