Functions as an U snRNP-specific nuclear import adapter. Involved in the trimethylguanosine (m3G)-cap-dependent nuclear import of U snRNPs. Binds specifically to the terminal m3G-cap U snRNAs. Interacts with components of the snRNP complex including SmB and Smn; these interactions are RNA-dependent. Interacts with importin-7 msk but not with importin subunit beta Fs(2)Ket; the interaction is RNA-dependent. Mostly localized to the nuclear periphery. In Malpighian tubule cells, detected in nuclear foci that include the Cajal bodies. Accumulates in the U bodies of the follicle and nurse cells. Expressed throughout development and in adults, with highest levels of expression during embryogenesis. Belongs to the snurportin family.