U2 small nuclear RNA is remarkably conserved between Schizosaccharomyces pombe and mammals.

We report the molecular cloning and sequencing of the most abundant trimethylguanosine-capped small nuclear RNA from the fission yeast Schizosaccharomyces pombe, a highly conserved homolog of mammalian U2 small nuclear RNA. This RNA is 186 nucleotides in length, just 2 nucleotides shorter than its human counterpart; this is in contrast to Saccharomyces cerevisiae U2, which is 1,175 nucleotides long. Moreover, the secondary structure of Schizosaccharomyces pombe U2 is virtually identical to that of mammalian U2, including the 3' half of the RNA, which shows limited primary sequence identity. Northern (RNA) blot analysis revealed that the size of this RNA is conserved not only in fission yeasts but in many organisms, including other ascomycetes.