Point mutation analysis of the Xenopus laevis RNA polymerase I core promoter.
The core region of the Xenopus laevis pre-ribosomal RNA promoter was subjected to point mutation analysis. A total of 27 point mutants within a 78 base pair region from -64 to +14, (relative to the start of transcription at +1), were assayed by oocyte microinjection. The results locate the 3' boundary of the core promoter at +4 and the 5' boundary at between -33 and -39 and suggest that this region of the Xenopus promoter is generally similar in organisation to mammalian core promoters. In particular, the conserved guanidine nucleotides at -7 and -16 are clearly essential for promoter function. The data suggest that interactions between the transcription machinery and the promoter occur in four distinct regions around +2 to +4, -7, -17 to -20 and -28 to -33. This particular periodicity of functionally important nucleotides is consistent with a model in which all protein-DNA interactions take place from predominantly one side of the DNA helix.
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Biophysics Laboratories, Portsmouth Polytechnic, UK.
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Smith
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D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004275:DNA, Ribosomal / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013379:Substrate Specificity; D014982:Xenopus laevis / Q000235:genetics
D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012318:RNA Polymerase I