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.
Mesh Terms:
Amino Acid Sequence, Animals, Base Sequence, Cloning, Molecular, DNA, Complementary, DNA-Binding Proteins, Drosophila melanogaster, Humans, Mice, Molecular Sequence Data, RNA Polymerase I, RNA Precursors, RNA-Binding Proteins, Recombinant Fusion Proteins, Transcription, Genetic
Date: May. 15, 1998
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