Figure 2.

Regulation of ARF protein accumulation and nucleo-cytoplasmic partitioning by ubiquitylation, SUMOylation, and phosphorylation. (A) SCF^AFF1 directly interacts with ARF7 and ARF19, and perhaps additional ARFs, to promote ARF degradation and/or nuclear import, likely by promoting distinct ubiquitin moieties to regulate ARF degradation and/or nuclear import. Several possible biological functions for ARF ubiquitylation include: 1) removal of unnecessary ARF protein; 2) regulation of the Class-A and B/C ARF competition; and 3) Environmental responses. (B). SUMOylation of ARF7 and MdARF8 regulate lateral root development. (C) Phosphorylation of ARF2 and SlARF4 block their DNA-binding activity; however, phosphorylation of ARF7 and ARF19 increase the DNA-binding capacity.