scholarly journals Loss of the Rpb4/Rpb7 Subcomplex in a Mutant Form of the Rpb6 Subunit Shared by RNA Polymerases I, II, and III

2003 ◽  
Vol 23 (9) ◽  
pp. 3329-3338 ◽  
Author(s):  
Qian Tan ◽  
Meredith H. Prysak ◽  
Nancy A. Woychik
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerases ◽  
Mutant Form ◽  
Direct Association ◽  
Before And After ◽  
Polymerase I ◽  
Conserved Core ◽  
Mutant Cells ◽  
Regulation Of Enzyme Activity

ABSTRACT We have identified a conditional mutation in the shared Rpb6 subunit, assembled in RNA polymerases I, II, and III, that illuminated a new role that is independent of its assembly function. RNA polymerase II and III activities were significantly reduced in mutant cells before and after the shift to nonpermissive temperature. In contrast, RNA polymerase I was marginally affected. Although the Rpb6 mutant strain contained two mutations (P75S and Q100R), the majority of growth and transcription defects originated from substitution of an amino acid nearly identical in all eukaryotic counterparts as well as bacterial ω subunits (Q100R). Purification of mutant RNA polymerase II revealed that two subunits, Rpb4 and Rpb7, are selectively lost in mutant cells. Rpb4 and Rpb7 are present at substoichiometric levels, form a dissociable subcomplex, are required for RNA polymerase II activity at high temperatures, and have been implicated in the regulation of enzyme activity. Interaction experiments support a direct association between the Rpb6 and Rpb4 subunits, indicating that Rpb6 is one point of contact between the Rpb4/Rpb7 subcomplex and RNA polymerase II. The association of Rpb4/Rpb7 with Rpb6 suggests that analogous subunits of each RNA polymerase impart class-specific functions through a conserved core subunit.

The yeast alpha 2 protein can repress transcription by RNA polymerases I and II but not III

1993 ◽  
Vol 13 (7) ◽  
pp. 4029-4038
Author(s):  
B M Herschbach ◽  
A D Johnson
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase Iii ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Cell Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Type Specific ◽  
Polymerase I ◽  
Rna Polymerase Ii Transcription

The alpha 2 protein of the yeast Saccharomyces cerevisiae normally represses a set of cell-type-specific genes (the a-specific genes) that are transcribed by RNA polymerase II. In this study, we determined whether alpha 2 can affect transcription by other RNA polymerases. We find that alpha 2 can repress transcription by RNA polymerase I but not by RNA polymerase III. Additional experiments indicate that alpha 2 represses RNA polymerase I transcription through the same pathway that it uses to repress RNA polymerase II transcription. These results implicate conserved components of the transcription machinery as mediators of alpha 2 repression and exclude several alternate models.

A Drosophila anti-RNA polymerase II antibody recognizes a plant nucleolar antigen, RNA polymerase I, which is mostly localized in fibrillar centres

1991 ◽  
Vol 100 (1) ◽  
pp. 99-107 ◽  
Author(s):  
M. Martin ◽  
F.J. Medina
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Large Subunit ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Dense Fibrillar Component ◽  
Transition Area ◽  
Fibrillar Component ◽  
Polymerase I

The distribution of nucleolar RNA polymerase in the nucleolus of onion root meristematic cells has been studied by means of an antibody originally raised against Drosophila RNA polymerase II. This antibody recognizes the homologous domains of the large subunit of the enzyme, which are highly conserved throughout evolution in the three classes of eucaryotic RNA polymerases. Given that RNA polymerase I is confined to the nucleolus, and that the onion cell nucleolus lacks digitations of extranucleolar chromatin, we conclude that the nucleolar enzyme localized is RNA polymerase I. A quantitative approach, independent of the existence of borderlines between nucleolar fibrillar centres and the dense fibrillar component, allowed us to show that the enzyme is localized in fibrillar centres and in the transition area between them and the dense fibrillar component, in parallel with the nucleolar DNA. These results, together with previous autoradiographic, cytochemical and immunocytochemical results, in this and other species, lead us to conclude that the activation of rDNA for transcription occurs in the fibrillar centres and pre-rRNA synthesis is expressed at the transition area between fibrillar centres and the dense fibrillar component. Fibrillar centres are connected to each other by extended RNA polymerase-bound DNA fibres, presumably active in transcription. This work provides evidence of the high evolutionary conservation of some domains of the large subunit of RNA polymerases and of the existence of fibrillar centres in the nucleolus of plant cells, totally homologous to those described in mammalian cells.

Purification and properties of RNA polymerases I and II from germinated spores of Rhizopus stolonifer

1974 ◽  
Vol 20 (9) ◽  
pp. 1267-1272 ◽  
Author(s):  
Cheng-Shung Gong ◽  
James L. Van Etten
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerases ◽  
Molecular Structures ◽  
Rhizopus Stolonifer ◽  
Mycelial Fungus ◽  
Molecular Weights ◽  
Purification And Properties ◽  
Eukaryotic Organisms ◽  
Polymerase I

RNA polymerases I and II were purified several hundredfold from germinated spores of the mycelial fungus, Rhizopus stolonifer. Three major subunit proteins with estimated molecular weights of 180 000, 104 000, and 32 000 daltons were obtained from RNA polymerase I and four major subunit proteins with estimated molecular weights of 215 000, 114 000, 37 000, and 27 000 daltons were obtained from RNA polymerase II. Therefore, the molecular structures of RNA polymerases I and II from R. stolonifer are essentially similar to those purified from other eukaryotic organisms.

scholarly journals The yeast alpha 2 protein can repress transcription by RNA polymerases I and II but not III.

1993 ◽  
Vol 13 (7) ◽  
pp. 4029-4038 ◽  
Author(s):  
B M Herschbach ◽  
A D Johnson
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase Iii ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Cell Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Type Specific ◽  
Polymerase I ◽  
Rna Polymerase Ii Transcription

The alpha 2 protein of the yeast Saccharomyces cerevisiae normally represses a set of cell-type-specific genes (the a-specific genes) that are transcribed by RNA polymerase II. In this study, we determined whether alpha 2 can affect transcription by other RNA polymerases. We find that alpha 2 can repress transcription by RNA polymerase I but not by RNA polymerase III. Additional experiments indicate that alpha 2 represses RNA polymerase I transcription through the same pathway that it uses to repress RNA polymerase II transcription. These results implicate conserved components of the transcription machinery as mediators of alpha 2 repression and exclude several alternate models.

Control points in eucaryotic ribosome biogenesis

1991 ◽  
Vol 69 (1) ◽  
pp. 5-22 ◽  
Author(s):  
D. E. Larson ◽  
P. Zahradka ◽  
B. H. Sells
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Rna Polymerase Iii ◽  
Ribosomal Subunits ◽  
Rrna Species ◽  
Polymerase I ◽  
Ribosomal Precursor ◽  
Precursor Molecules

Ribosome biogenesis in eucaryotic cells involves the coordinated synthesis of four rRNA species, transcribed by RNA polymerase I (18S, 28S, 5.8S) and RNA polymerase III (5S), and approximately 80 ribosomal proteins translated from mRNAs synthesized by RNA polymerase II. Assembly of the ribosomal subunits in the nucleolus, the site of 45S rRNA precursor gene transcription, requires the movement of 5S rRNA and ribosomal proteins from the nucleoplasm and cytoplasm, respectively, to this structure. To integrate these events and ensure the balanced production of individual ribosomal components, different strategies have been developed by eucaryotic organisms in response to a variety of physiological changes. This review presents an overview of the mechanisms modulating the production of ribosomal precursor molecules and the rate of ribosome biogenesis in various biological systems.Key words: rRNA, ribosomal proteins, nucleolus, ribosome.

Evidence that the SKI antiviral system of Saccharomyces cerevisiae acts by blocking expression of viral mRNA

1993 ◽  
Vol 13 (7) ◽  
pp. 4331-4341
Author(s):  
W R Widner ◽  
R B Wickner
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Copy Number ◽  
Dsrna Virus ◽  
Cdna Clones ◽  
Viral Mrnas ◽  
Nucleolar Proteins ◽  
Toxin Secretion ◽  
Polymerase I ◽  
Beta Galactosidase

The SKI2 gene is part of a host system that represses the copy number of the L-A double-stranded RNA (dsRNA) virus and its satellites M and X dsRNA, of the L-BC dsRNA virus, and of the single-stranded replicon 20S RNA. We show that SKI2 encodes a 145-kDa protein with motifs characteristic of helicases and nucleolar proteins and is essential only in cells carrying M dsRNA. Unexpectedly, Ski2p does not repress M1 dsRNA copy number when M1 is supported by aN L-A cDNA clone; nonetheless, it did lower the levels of M1 dsRNA-encoded toxin produced. Since toxin secretion from cDNA clones of M1 is unaffected by Ski2p, these data suggest that Ski2p acts by specifically blocking translation of viral mRNAs, perhaps recognizing the absence of cap or poly(A). In support of this idea, we find that Ski2p represses production of beta-galactosidase from RNA polymerase I [no cap and no poly(A)] transcripts but not from RNA polymerase II (capped) transcripts.

Sign in / Sign up

Export Citation Format

Share Document