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. 2018 Nov 2;179(1):168–183. doi: 10.1104/pp.18.00910

Figure 4.

Figure 4.

Formation of COP1 + SUMO1∙SIZ1-containing NBs depends on the COP1 substrate-binding pocket that apparently recruits SIZ1 via VP motifs. A, Nuclear localization pattern of the SUMO1∙SIZ1 BiFC pair in cells overexpressing RFP-COP1 variants: COP1SUMO, COP1RING, and COP1SUBSTRATE. See Figure 3A for details on the COP1 variants. Micrographs show from top to bottom the BiFC signal, RFP-COP1, and their merged signals. Conditions were identical to those in Figure 1. Scale bars, 10 µm. B, Schematic representation of SIZ1 variants and the protein-protein interaction domain disrupted (left side) by the mutations introduced: plant homeodomain (PHD) and Pro-Ile-Asn-Ile-Thr (PINIT), both reduced substrate binding; SP-RING, no interaction with SCE1; VP1 and VP2, putative interacting motifs for the COP1 substrate binding groove. C, Mapping of the COP1 interaction site in SIZ1 using Y2H analysis of the SIZ1 variants depicted in B. Similar to that in Figure 3, SIZ1 variants were fused to GAL4 AD-fusion, whereas COP1 was fused to GAL4 BD. Yeast growth was scored after 3 d at 30°C.