Figure 6.

K578 is a key CtIP SUMOylation site. (A) Schematic diagrams of CtIP domain structure of wildtype (WT) CtIP and relevant phosphorylation and SUMOylation sites in this study, along with residues substituted in the corresponding site mutants of GFP-tagged CtIP. ‘Tet’: tetramerization domain; ‘dimeriz’: dimerization domain; ‘nuclease’: endonuclease domain, ‘PCNA interaction’: also known as PIP-Box. In (B–E), HeLa His₁₀-SUMO-2 cells were synchronized to mid-S phase. 24 h prior to harvest, they were transfected with the indicated GFP-CtIP constructs, then portioned into input control and His pull-down (His PD) fractions and processed accordingly. * indicates an exogenous CtIP immunoreactive band that is not of interest; it may be lower molecular weight SUMO-2-modified CtIP, or unmodified GFP-CtIP retained in the His PD fraction due to high expression. (B) Shown is a representative result of three independent experiments. (C) The solid line defines where an intervening lane was spliced out of the image. Shown is a representative result of three independent experiments. (D) Shown is a representative result of two independent experiments. (E) Shown is a representative result of three independent experiments.