title: The ribosomal spacer in Xenopus laevis is transcribed as part of the primary ribosomal RNA.
abstract: S1 mapping of Xenopus laevis ribosomal RNA transcripts, both in oocyte microinjection experiments and in vivo, shows that all but 212 bp of the so-called "non-transcribed" spacer (NTS) of the ribosomal DNA repeat is transcribed as part of the primary ribosomal transcript. The 40S pre-ribosomal RNA (pre-rRNA) is therefore a processing intermediate. The primary ribosomal transcript co-terminates with the previously described spacer transcripts [Moss], at a site 213 bp upstream of the 40S pre-rRNA initiation site. This mode of transcription suggests a simple mechanism for the recently proposed phenomenon of "readthrough-enhancement", [Moss et al, Moss], where readthrough transcription from an upstream gene may enhance transcription of a gene immediately downstream in the tandem ribosomal repeat.
mesh_terms: D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant; D004275:DNA, Ribosomal / Q000235:genetics*; D005260:Female; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D014158:Transcription, Genetic; D014982:Xenopus laevis / Q000235:genetics*
chemical_list: D004274:DNA, Recombinant; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D004262:DNA Restriction Enzymes