Spacer promoters are essential for efficient enhancement of X. laevis ribosomal transcription.
The X. laevis ribosomal DNA spacer contains duplicated RNA polymerase I "spacer promoters" and an array of repeated 60/81 bp promoter-related sequences. The latter have been shown to enhance transcription from a 40S preribosomal RNA promoter in cis. Here we present evidence that at least one spacer promoter is also necessary for efficient enhancement. Deletion of the spacer promoter sequences in a construct carrying only one such promoter reduces 40S RNA transcription to approximately 10% of wild type. This effect apparently is caused by inactivation of the spacer promoter, since mutants in which 4-177 bp of the spacer promoter and adjacent sequences are deleted are functionally equivalent. Spacer promoters and 60/80 bp arrays therefore probably act together to enhance 40S pre-RNA transcription in X. laevis.
D000818:Animals; D002874:Chromosome Mapping; D004275:DNA, Ribosomal / Q000235:genetics*; D005786:Gene Expression Regulation; D009154:Mutation; D011401:Promoter Regions, Genetic; D012335:RNA, Ribosomal / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D014982:Xenopus laevis / Q000235:genetics*
D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D014157:Transcription Factors