Open AccessA shared subunit belongs to the eukaryotic core RNA polymerase.
Author(s) -
Martin Lanzendörfer,
Amke Smid,
Claudia Klinger,
Patrick Schultz,
A Sentenac,
Christophe Carles,
Michel Riva
Publication year - 1997
Publication title -
genes and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.136
H-Index - 438
eISSN - 1549-5477
pISSN - 0890-9369
DOI - 10.1101/gad.11.8.1037
Subject(s) - biology , rna polymerase i , transcription (linguistics) , rna polymerase ii , protein subunit , rna , rna polymerase , microbiology and biotechnology , specificity factor , rna polymerase iii , polymerase , enzyme , biochemistry , rna dependent rna polymerase , gene expression , gene , promoter , linguistics , philosophy
The yeast RNA polymerase I is a multimeric complex composed of 14 distinct subunits, 5 of which are shared by the three forms of nuclear RNA polymerase. The reasons for this structural complexity are still largely unknown. Isolation of an inactive form of RNA Pol I lacking the A43, ABC23, and A14 subunits (RNA Pol I delta) allowed us to investigate the function of the shared subunit ABC23 by in vitro reconstitution experiments. Addition of recombinant ABC23 alone to the RNA Pol I delta reactivated the enzyme to up to 50% of the wild-type enzyme activity. The recombinant subunit was stably and stoichiometrically reassociated within the enzymatic complex. ABC23 was found to be required for the formation of the first phosphodiester bond, but it was not involved in DNA binding by RNA Pol I, as shown by gel retardation and surface plasmon resonance experiments, and did not recycle during transcription. Electron microscopic visualization and electrophoretic analysis of the subunit depleted and reactivated forms of the enzyme indicate that binding of ABC23 caused a major conformational change leading to a transcriptionally competent enzyme. Altogether, our results demonstrate that the ABC23 subunit is required for the structural and functional integrity of RNA Pol I and thus should be considered as part of the core enzyme.