Molecular coevolution of mammalian ribosomal gene terminator sequences and the transcription termination factor TTF-I.
Both the DNA elements and the nuclear factors that direct termination of ribosomal gene transcription exhibit species-specific differences. Even between mammals--e.g., human and mouse--the termination signals are not identical and the respective transcription termination factors (TTFs) which bind to the terminator sequence are not fully interchangeable. To elucidate the molecular basis for this species-specificity, we have cloned TTF-I from human and mouse cells and compared their structural and functional properties. Recombinant TTF-I exhibits species-specific DNA binding and terminates transcription both in cell-free transcription assays and in transfection experiments. Chimeric constructs of mouse TTF-I and human TTF-I reveal that the major determinant for species-specific DNA binding resides within the C terminus of TTF-I. Replacing 31 C-terminal amino acids of mouse TTF-I with the homologous human sequences relaxes the DNA-binding specificity and, as a consequence, allows the chimeric factor to bind the human terminator sequence and to specifically stop rDNA transcription.
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Division of Molecular Biology of the Cell II, German Cancer Research Center, Heidelberg.
Grummt
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D005075:Biological Evolution; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D006367:HeLa Cells; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D008322:Mammals / Q000235:genetics*; D051379:Mice / Q000235:genetics*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010454:Peptide Termination Factors / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012335:RNA, Ribosomal / Q000096:biosynthesis* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013728:Terminator Regions, Genetic; D014157:Transcription Factors; D014158:Transcription, Genetic
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D010454:Peptide Termination Factors; D012335:RNA, Ribosomal; D011993:Recombinant Fusion Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors; C504004:Ttf1 protein, mouse