PRIMARY STRUCTURE OF THE CANINE U1 SNRNA

The nucleotide (nt) sequence of the canine U1 snRNA was determined. It exhibited significant homology (90-98%) with known U1 sequences, The RNA can be folded according to the secondary structure previously prop osed for the U1 snRNA, It contained the conserved sequence UUACCUG in loop A (nt 6-12), required for the recognition of the 5' splice site, and the sequence UGCACU in loop B (nt 68-73), required for recognition of the U1-70K protein. The U1 snRNA was localized in the nucleus and its transcription was sensitive to a-amanitin, suggesting that it is t ranscribed by RNA polymerase II, Southern analysis revealed that the c anine genome possesses 5-10 copies of U1 snRNA-encoding genes.