Virtually the entire Xenopus laevis rDNA multikilobase intergenic spacer serves to stimulate polymerase I transcription

Edward B. Mougey, Louise K. Pape, Barbara Sollner-Webb

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The promoter-distal half of the spacer separating the tandem Xenopus laevis rRNA genes consists of '0' and '1' repetitive elements that have been considered unimportant in polymerase I transcriptional activation. Utilizing oocyte microinjection, we now demonstrate that the 0/1 region, as well as its component 0 and 1 repeats, substantially stimulate transcription from a ribosomal promoter in cis and inhibit transcription when located in trans. Both the cis and trans responses increase linearly with increasing numbers of 0 or 1 repeats until saturation is approached. The 0/1 block and its component elements stimulate transcription in both orientations, over distances, and when placed downstream of the initiation site, properties for which the 60/81-base pair (bp) repeats have been defined as polymerase I enhancers. In their natural promoter-distal rDNA location, the 0/1 repeats can stimulate transcription from the rRNA gene promoter, above the level afforded by the intervening 60/81-bp repeats and spacer promoter. In addition, as with the 60/81-bp repeats, the 0/1 repeats bind a factor in common with the rDNA promoter. Thus, the entire X. laevis rDNA intergenic spacer (the 0 repeats, 1 repeats, spacer promoter repeats, and 60/81-bp repeats) acts together to enhance ribosomal transcription.

Original languageEnglish (US)
Pages (from-to)27138-27145
Number of pages8
JournalJournal of Biological Chemistry
Issue number43
StatePublished - 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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