Abstract
Cells carefully modulate the rate of rRNA transcription in order to prevent an overinvestment in ribosome synthesis under less favorable nutritional conditions. In mammals, growth-dependent regulation of RNA polymerase I (Pol I) transcription is mediated by TIF-IA, an essential initiation factor that is active in extracts from growing but not starved or cycloheximide-treated mammalian cells. Here we report the molecular cloning and functional characterization of recombinant TIF-IA, which turns out to be the mammalian homolog of the yeast factor Rrn3p. We demonstrate that TIF-IA interacts with Pol I in the absence of template DNA, augments Pol I transcription in vivo and rescues transcription in extracts from growth-arrested cells in vitro.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3T3 Cells
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Amino Acid Sequence
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Animals
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Blotting, Western
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Cloning, Molecular
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Genes, Reporter / genetics
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HeLa Cells
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Humans
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Mice
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Microscopy, Fluorescence
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Molecular Sequence Data
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Plasmids / genetics
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Plasmids / metabolism
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Pol1 Transcription Initiation Complex Proteins*
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RNA, Ribosomal / biosynthesis*
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RNA, Ribosomal / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae Proteins*
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Sequence Alignment
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Transcription Factors / chemistry
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Transcription Factors / genetics*
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Transcription Factors / metabolism
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Transfection
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Yeasts / genetics
Substances
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Pol1 Transcription Initiation Complex Proteins
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RNA, Ribosomal
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RRN3 protein, S cerevisiae
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RRN3 protein, human
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Rrn3 protein, mouse
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Saccharomyces cerevisiae Proteins
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Transcription Factors