
ABSTRACT Maf1 is a highly conserved central regulator of transcription by RNA polymerase III (Pol III), and Maf1 activity influences a wide range of phenotypes from metabolic efficiency to lifespan. Here, we present a 3.3 Å cryo-EM structure of yeast Maf1 bound to Pol III, which establishes how Maf1 achieves transcription repression. In the Maf1-bound state, Pol III elements that are involved in transcription initiation are sequestered, and the active site is sealed off due to ordering of the mobile C34 winged helix 2 domain. Specifically, the Maf1 binding site overlaps with the binding site of the Pol III transcription factor TFIIIB and DNA in the pre-initiation complex, rationalizing that binding of Maf1 and TFIIIB to Pol III are mutually exclusive. We validate our structure using variants of Maf1 with impaired transcription-inhibition activity. These results reveal the exact mechanism of Pol III inhibition by Maf1, and rationalize previous biochemical data.
Models, Molecular, Protein Conformation, alpha-Helical, Binding Sites, Saccharomyces cerevisiae Proteins, Cryoelectron Microscopy, Genetic Vectors, Gene Expression, RNA Polymerase III, Saccharomyces cerevisiae, Article, Recombinant Proteins, Repressor Proteins, Protein Subunits, Escherichia coli, Humans, Protein Conformation, beta-Strand, Protein Interaction Domains and Motifs, Amino Acid Sequence, Cloning, Molecular, Sequence Alignment, Protein Binding
Models, Molecular, Protein Conformation, alpha-Helical, Binding Sites, Saccharomyces cerevisiae Proteins, Cryoelectron Microscopy, Genetic Vectors, Gene Expression, RNA Polymerase III, Saccharomyces cerevisiae, Article, Recombinant Proteins, Repressor Proteins, Protein Subunits, Escherichia coli, Humans, Protein Conformation, beta-Strand, Protein Interaction Domains and Motifs, Amino Acid Sequence, Cloning, Molecular, Sequence Alignment, Protein Binding
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