Do snRNAs exit the nucleus or not?
After transcription of some UsnRNAs, the RNAs leave nuclei first. After assembly of various proteins and modification on the RNAs in cytosol, the RNAs come back to nuclei. In addition, it has been shown that mature U6snRNP shuttles between nuclear and cytosolic fractions in yeasts, if I remember correctly.

http://openi.nlm.nih.gov/detailedresult.php?img=2582628_gkn658f1&amp;req=4