抄録
Species, structure and proposed function of the heterogeneous, low-molecular-weight nuclear RNAs (sn RNA) (65-300 nucleotides) which are not directly involved in protein synthesis, are reviewed.
The RNAs mainly contain two families of RNA: One has an unusual, trimethyl guanine (m32, 2, 7G) at the 5' end of molecule, some monomethylated bases and/or pseudouracil. The other family of RNAs of which 5' end is pppGp' has no modified bases. These RNAs appear to be the products by DNA-dependent RNA polymerase I or III.
Several presumptive models are summarized, which are presented for regulation by snRNA of transcription, splicing and/or selection of mRNA on ribosomes based on snRNA-DNA and/or snRNA-gene transcripts interaction.
