title: Excess 5'-terminal sequences in the rat nucleolar 28S ribosomal RNA.
abstract: The 5'-termini of purified rat liver nucleolar and cytoplasmic 28S ribosomal RNA (rRNA) are precisely located within the homologous rDNA sequence by S1 nuclease protection mapping using an appropriate rDNA restriction fragment. The 5'-termini of nucleolar 28S rRNA are heterogeneous in length. The bulk of the nucleolar 28S rRNA map within two CTC motifs in rDNA located in the internal transcribed spacer 2 at the 50-60 and 5-15 bp upstream from the site of the homogeneous 5'-terminus of the cytoplasmic 28S rRNA. These results provide direct proof that nucleolar 28S rRNA molecules contain excess sequences at their 5'-termini and require further processing to generate the mature cytoplasmic 28S rRNA.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002466:Cell Nucleolus / Q000032:analysis*; D004247:DNA / Q000032:analysis; D004275:DNA, Ribosomal; D004720:Endonucleases; D008099:Liver / Q000032:analysis; D008297:Male; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal / Q000302:isolation & purification*; D051381:Rats; D011919:Rats, Inbred Strains; D015719:Single-Strand Specific DNA and RNA Endonucleases
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D004247:DNA; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases