Cloning and functional characterization of PTRF, a novel protein which induces dissociation of paused ternary transcription complexes.
Termination of transcription by RNA polymerase I (Pol I) is a two-step process which involves pausing of elongating transcription complexes and release of both pre-rRNA and Pol I from the template. In mouse, pausing of elongation complexes is mediated by the transcription termination factor TTF-I bound to the 'Sal box' terminator downstream of the rDNA transcription unit. Dissociation of paused ternary complexes requires a cellular factor, termed PTRF for Pol I and transcript release factor. Here we describe the molecular cloning of a cDNA corresponding to murine PTRF. Recombinant PTRF is capable of dissociating ternary Pol I transcription complexes in vitro as revealed by release of both Pol I and nascent transcripts from the template. Consistent with its function in transcription termination, PTRF interacts with both TTF-I and Pol I. Moreover, we demonstrate specific binding of PTRF to transcripts containing the 3' end of pre-rRNA. Substitution of 3'-terminal uridylates by guanine residues abolishes PTRF binding and impairs release activity. The results reveal a network of protein-protein and protein-nucleic acid interactions that governs termination of Pol I transcription.
Jansa
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P
Division of Molecular Biology of the Cell II, German Cancer Research Center, Heidelberg, Germany.
Mason
S W
SW
Hoffmann-Rohrer
U
U
Grummt
I
I
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster; D006801:Humans; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D012318:RNA Polymerase I / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
C112745:Cavin1 protein, mouse; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors; C504004:Ttf1 protein, mouse; D012318:RNA Polymerase I