Nucleotide sequence of nuclear 5.4 S RNA of mouse cells

The nucleotide sequence of nuclear 5.4 S RNA, a new species of small nuclear RNA (snRNA) of mouse cells, was determined. The 5.4 S RNA consists of 138 nucleotide residues containing 1 mol each of 2,2,7-trimethylguanosine (m^2,2,7₃ G), 2′-O-methyladenosine (Am), 2′-O-methyluridine (Um) and pseudouridine as modified nucleosides. This RNA has a cap structure, m^2,2,7₃ GpppAm-, at its 5′-terminus and sequences complementary to the terminal consensus sequences of introns. The sequence complementary to the 5′-splice junction, A-U-C-C-ψ-U-A-C-C-U-G, is very similar to the 5′-terminal sequence of U1 RNA.