E3 SUMO-protein ligase which facilitates SUMO1 and SUMO2 conjugation by UBE2I. Involved in transport factor (Ran-GTP, karyopherin)-mediated protein import via the F-G repeat-containing domain which acts as a docking site for substrates. Component of the nuclear export pathway. Specific docking site for the nuclear export factor exportin-1. Inhibits EIF4E-dependent mRNA export. Sumoylates PML at 'Lys-490' which is essential for the proper assembly of PML-NB. Recruits BICD2 to the nuclear envelope and cytoplasmic stacks of nuclear pore complex known as annulate lamellae during G2 phase of cell cycle (By similarity). Binds single-stranded RNA (in vitro) . Probable inactive PPIase with no peptidyl-prolyl cis-trans isomerase activity.
Subcellular locations: Nucleus, Nucleus membrane, Nucleus, Nuclear pore complex, Nucleus envelope
Detected in diffuse and discrete intranuclear foci. Cytoplasmic filaments.