Nuclear complexes that contain E2Fs interact with RING3. A, diagram of COOH-terminal deletions of RING3 N-tagged with six histidines (ΔSnaBI, ΔBspMI, ΔBalI, ΔHindIII, ΔPstI, and ΔAccI), with the number of amino acids in RING3 shown on a scale (above). B, input HeLa nuclear extract (Lane 1) and eluted proteins (Lanes 2 and 3) from a nonimmune rabbit IgG affinity column (Lane 2) or αRING3 rabbit IgG affinity column (Lane 3) were separated by SDS-PAGE, electroblotted to PVDF, and probed with rabbit polyclonal antibody specific for all E2Fs (arrow). C, HeLa nuclear proteins were eluted from Ni-NTA columns charged with wild-type recombinant RING3 protein or with equal moles of the deletion mutants listed in A. Eluted fractions were immunoblotted with anti-E2F-1 or anti-E2F-2.