[8][10] IPO13 is broadly expressed in a variety of tissues in the human body, including the heart,[11] cornea,[11] fetal lung,[11] brain,[11] endometrial carcinoma,[11] and testes.

[8][9][12] Importin-β-like factors are the largest class of NTRs and are classified as importins or exportins based on the direction of cargo transport and their response to the RanGTP gradient across the nuclear envelope.

[10] Low total or active concentrations of importin-13 in the nucleus show that importin-13 is a rate-limiting factor for nuclear import and export of cargo proteins.

[8] Other known importin-13 import cargoes are MAGOH,[8] NFYB,[8] DR1,[8] DRAP1,[8] RBM8,[14] paired type homeodomain transcription factors (TFs),[14] myopodinm,[14] the glucocorticoid receptor (GR),[14] RFPL3,[11] and the RBM8-MGN complex.

[13] Walter et al. demonstrated that importin-13 mediates the nuclear import of the histone fold pairs CHRAC-15/17 and p12/CHRAC-17 only in the heterodimerized forms of these substrates.