Natural point mutations within rat rDNA transcription terminator elements reveal the functional importance of single bases for factor binding and termination.
The rat rDNA transcription unit extends 560-565 bp into the spacer downstream of the 28S rRNA coding region. The site of 3' end formation is located in front of a conserved 18 bp sequence element which is repeated eight times in the 3' spacer between nucleotides +582 and +1767 relative to the 3' terminus of 28S rRNA. These sequence motifs are almost identical to the RNA polymerase I transcription termination signal (the Sal I box) that has previously been identified in the 3' terminal spacer of mouse rDNA. Interestingly, each of the single rat elements contains one or more base substitutions as compared to the murine Sal I box. Individual rat Sal I boxes were cloned and tested for their ability to interact with the murine termination factor and to direct transcription termination. It is shown that five of the eight boxes represent genuine transcription terminators, while three elements contain certain point mutations which are not recognized by the nuclear Sal I box-binding protein and therefore are functionally inactive.Images
D000818:Animals; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D005809:Genes, Regulator; D051379:Mice / Q000235:genetics; D009154:Mutation; D009694:Nucleic Acid Precursors / Q000096:biosynthesis; D012318:RNA Polymerase I / Q000378:metabolism; D012322:RNA Precursors; D012335:RNA, Ribosomal / Q000096:biosynthesis; D051381:Rats / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D013728:Terminator Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D009694:Nucleic Acid Precursors; D012322:RNA Precursors; D012335:RNA, Ribosomal; D014157:Transcription Factors; D012318:RNA Polymerase I