GADD45A binds PCNA homotrimer (Smith et al. 1994, Hall et al. 1995, Sanchez et al. 2010). The consequences of this interaction are not clear. Binding to GADD45A may negatively regulate PCNA-mediated DNA synthesis during S phase of the cell cycle or it may promote PCNA-mediated DNA repair synthesis (Smith et al. 1994, Kim et al. 2013).