Enhancers for RNA polymerase I in mouse ribosomal DNA.
The intergenic spacer of the mouse ribosomal genes contains repetitive 140-base-pair (bp) elements which we show are enhancers for RNA polymerase I transcription analogous to the 60/81-bp repetitive enhancers (enhancers containing a 60-bp and an 81-bp element) previously characterized from Xenopus laevis. In rodent cell transfection assays, the 140-bp repeats stimulated an adjacent mouse polymerase I promoter when located in cis and competed with it when located in trans. Remarkably, in frog oocyte injection assays, the 140-bp repeats enhanced a frog ribosomal gene promoter as strongly as did the homologous 60/81-bp repeats. Mouse 140-bp repeats also competed against frog promoters in trans. The 140-bp repeats bound UBF, a DNA-binding protein we have purified from mouse extracts that is the mouse homolog of polymerase I transcription factors previously isolated from frogs and humans. The DNA-binding properties of UBF are conserved from the mouse to the frog. The same regulatory elements (terminators, gene and spacer promoters, and enhancers) have now been identified in both a mammalian and an amphibian spacer, and they are found in the same relative order. Therefore, this arrangement of elements probably is widespread in nature and has important functional consequences.
Pikaard
C S
CS
Basic Sciences Division, Hutchinson Cancer Research Center, Seattle, Washington 98104.
Pape
L K
LK
Henderson
S L
SL
Ryan
K
K
Paalman
M H
MH
Lopata
M A
MA
Reeder
R H
RH
Sollner-Webb
B
B
D000818:Animals; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D051379:Mice; D008969:Molecular Sequence Data; D009710:Nucleotide Mapping; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D014982:Xenopus laevis
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D012335:RNA, Ribosomal; D012318:RNA Polymerase I