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The recruitment of RNA polymerase I on rDNA is mediated by the interaction of the A43 subunit with Rrn3
Author(s) -
Peyroche Gérald,
Milkereit Philipp,
Bischler Nicolas,
Tschochner Herbert,
Schultz Patrick,
Sentenac André,
Carles Christophe,
Riva Michel
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.20.5473
Subject(s) - biology , rna polymerase , rna polymerase i , protein subunit , polymerase , microbiology and biotechnology , ribosomal rna , rna polymerase ii , rna , rna dependent rna polymerase , genetics , gene , gene expression , promoter
RNA polymerase I (Pol I) is dedicated to transcription of the large ribosomal DNA (rDNA). The mechanism of Pol I recruitment onto rDNA promoters is poorly understood. Here we present evidence that subunit A43 of Pol I interacts with transcription factor Rrn3: conditional mutations in A43 were found to disrupt the transcriptionally competent Pol I–Rrn3 complex, the two proteins formed a stable complex when co‐expressed in Escherichia coli , overexpression of Rrn3 suppressed the mutant phenotype, and A43 and Rrn3 mutants showed synthetic lethality. Consistently, immunoelectron microscopy data showed that A43 and Rrn3 co‐localize within the Pol I–Rrn3 complex. Rrn3 has several protein partners: a two‐hybrid screen identified the C‐terminus of subunit Rrn6 of the core factor as a Rrn3 contact, an interaction supported in vitro by affinity chromatography. Our results suggest that Rrn3 plays a central role in Pol I recruitment to rDNA promoters by bridging the enzyme to the core factor. The existence of mammalian orthologues of A43 and Rrn3 suggests evolutionary conservation of the molecular mechanisms underlying rDNA transcription in eukaryotes.