Acts as a signaling molecule that communicates proliferative growth signals from the cytoplasm to the nucleus. Plays a role for the localization and accumulation of the survival motor neuron protein SMN1 in sub-nuclear bodies, including gems and Cajal bodies. Induces neuron differentiation and stimulates axonal growth and formation of growth cone in spinal cord motor neurons. Plays a role in the splicing of cellular pre-mRNAs. May be involved in H(2)O(2)-induced neuronal cell death (By similarity). Component of an import snRNP complex composed of KPNB1, SNUPN, SMN1 and ZNF259. Interacts (via C-terminal region) with SMN1 (via C-terminal region); the interaction occurs after treatment with serum. Interacts with elongation factor 1-alpha EEF1A1; the interaction occurs in a epidermal growth factor (EGF)-dependent manner. Interacts (via zinc fingers) with EGFR (via C-terminal cytoplasmic kinase domain); the interaction is negatively regulated in response to epidermal growth factor (EGF) stimulation and EGFR kinase activity. May also bind to the PDGFR receptor (By similarity). Localized predominantly in the cytoplasm in serum-starved cells growth arrested in G0 of the mitotic cell cycle. Localized both in the nucleus and cytoplasm at the G1 phase of the mitotic cell cycle. Accumulates in the subnuclear bodies during progression into the S phase of the mitotic cell cycle. Diffusely localized throughout the cell during mitosis. Colocalized with NPAT and SMN1 in nuclear bodies including gems (Gemini of coiled bodies) and Cajal bodies in a cell cycle-dependent manner. Colocalized with EGFR in the cytoplasm of quiescent cells. Translocates from the cytoplasm to the nucleus in a epidermal growth factor (EGF)-dependent manner. Translocates together with EEF1A1 from the cytoplasm to the nucleolus after treatment with mitogens. Colocalized with SMN1 in Gemini of coiled bodies (gems), Cajal bodies, axon and growth cones of neurons (By similarity). Belongs to the ZPR1 family.