Structural alterations of the nucleolus in mutants of Saccharomyces cerevisiae defective in RNA polymerase I

1993 ◽  
Vol 13 (4) ◽  
pp. 2441-2455
Author(s):  
M Oakes ◽  
Y Nogi ◽  
M W Clark ◽  
M Nomura
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Rrna Processing ◽  
Structural Element ◽  
Nucleolar Structure ◽  
Pol I ◽  
Polymerase I

We have previously constructed mutants of Saccharomyces cerevisiae in which the gene for the second-largest subunit of RNA polymerase I (Pol I) is deleted. In these mutants, rRNA is synthesized by RNA polymerase II from a hybrid gene consisting of the 35S rRNA coding region fused to the GAL7 promoter on a plasmid. These strains thus grow in galactose but not glucose media. By immunofluorescence microscopy using antibodies against the known nucleolar proteins SSB1 and fibrillarin, we found that the intact crescent-shaped nucleolar structure is absent in these mutants; instead, several granules (called mininucleolar bodies [MNBs]) that stained with these antibodies were seen in the nucleus. Conversion of the intact nucleolar structure to MNBs was also observed in Pol I temperature-sensitive mutants at nonpermissive temperatures. These MNBs may structurally resemble prenucleolar bodies observed in higher eukaryotic cells and may represent a constituent of the normal nucleolus. Furthermore, cells under certain conditions that inhibit rRNA synthesis did not cause conversion of the nucleolus to MNBs. Thus, the role of Pol I in the maintenance of the intact nucleolar structure might include a role as a structural element in addition to (or instead of) a functional role to produce rRNA transcripts. Our study also shows that the intact nucleolar structure is not absolutely required for rRNA processing, ribosome assembly, or cell growth and that MNBs are possibly functional in rRNA processing in the Pol I deletion mutants.

scholarly journals Structural alterations of the nucleolus in mutants of Saccharomyces cerevisiae defective in RNA polymerase I.

1993 ◽  
Vol 13 (4) ◽  
pp. 2441-2455 ◽  
Author(s):  
M Oakes ◽  
Y Nogi ◽  
M W Clark ◽  
M Nomura
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Rrna Processing ◽  
Structural Element ◽  
Nucleolar Structure ◽  
Pol I ◽  
Polymerase I

We have previously constructed mutants of Saccharomyces cerevisiae in which the gene for the second-largest subunit of RNA polymerase I (Pol I) is deleted. In these mutants, rRNA is synthesized by RNA polymerase II from a hybrid gene consisting of the 35S rRNA coding region fused to the GAL7 promoter on a plasmid. These strains thus grow in galactose but not glucose media. By immunofluorescence microscopy using antibodies against the known nucleolar proteins SSB1 and fibrillarin, we found that the intact crescent-shaped nucleolar structure is absent in these mutants; instead, several granules (called mininucleolar bodies [MNBs]) that stained with these antibodies were seen in the nucleus. Conversion of the intact nucleolar structure to MNBs was also observed in Pol I temperature-sensitive mutants at nonpermissive temperatures. These MNBs may structurally resemble prenucleolar bodies observed in higher eukaryotic cells and may represent a constituent of the normal nucleolus. Furthermore, cells under certain conditions that inhibit rRNA synthesis did not cause conversion of the nucleolus to MNBs. Thus, the role of Pol I in the maintenance of the intact nucleolar structure might include a role as a structural element in addition to (or instead of) a functional role to produce rRNA transcripts. Our study also shows that the intact nucleolar structure is not absolutely required for rRNA processing, ribosome assembly, or cell growth and that MNBs are possibly functional in rRNA processing in the Pol I deletion mutants.

scholarly journals Assembly and Functional Organization of the Nucleolus: Ultrastructural Analysis ofSaccharomyces cerevisiaeMutants

2000 ◽  
Vol 11 (6) ◽  
pp. 2175-2189 ◽  
Author(s):  
Stéphanie Trumtel ◽  
Isabelle Léger-Silvestre ◽  
Pierre-Emmanuel Gleizes ◽  
Frédéric Teulières ◽  
Nicole Gas
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Functional Organization ◽  
Ultrastructural Localization ◽  
Rna Polymerase I ◽  
Wild Type ◽  
Rdna Transcription ◽  
Nucleolar Structure ◽  
Fibrillar Component ◽  
Polymerase I

Using Saccharomyces cerevisiae strains with genetically modified nucleoli, we show here that changing parameters as critical as the tandem organization of the ribosomal genes and the polymerase transcribing rDNA, although profoundly modifying the position and the shape of the nucleolus, only partially alter its functional subcompartmentation. High-resolution morphology achieved by cryofixation, together with ultrastructural localization of nucleolar proteins and rRNA, reveals that the nucleolar structure, arising upon transcription of rDNA from plasmids by RNA polymerase I, is still divided in functional subcompartments like the wild-type nucleolus. rRNA maturation is restricted to a fibrillar component, reminiscent of the dense fibrillar component in wild-type cells; a granular component is also present, whereas no fibrillar center can be distinguished, which directly links this latter substructure to rDNA chromosomal organization. Although morphologically different, the mininucleoli observed in cells transcribing rDNA with RNA polymerase II also contain a fibrillar subregion of analogous function, in addition to a dense core of unknown nature. Upon repression of rDNA transcription in this strain or in an RNA polymerase I thermosensitive mutant, the nucleolar structure falls apart (in a reversible manner), and nucleolar constituents partially relocate to the nucleoplasm, indicating that rRNA is a primary determinant for the assembly of the nucleolus.

scholarly journals The RNA polymerase I transcription machinery

2006 ◽  
Vol 73 ◽  
pp. 203-216 ◽  
Author(s):  
Jackie Russell ◽  
Joost C.B.M. Zomerdijk
Keyword(s):  
Rna Polymerase ◽  
Mammalian Cells ◽  
Growth Conditions ◽  
Rna Polymerase I ◽  
Cellular Growth ◽  
Rrna Synthesis ◽  
Transcription Machinery ◽  
Pol I ◽  
A Cell ◽  
Polymerase I

The rRNAs constitute the catalytic and structural components of the ribosome, the protein synthesis machinery of cells. The level of rRNA synthesis, mediated by Pol I (RNA polymerase I), therefore has a major impact on the life and destiny of a cell. In order to elucidate how cells achieve the stringent control of Pol I transcription, matching the supply of rRNA to demand under different cellular growth conditions, it is essential to understand the components and mechanics of the Pol I transcription machinery. In this review, we discuss: (i) the molecular composition and functions of the Pol I enzyme complex and the two main Pol I transcription factors, SL1 (selectivity factor 1) and UBF (upstream binding factor); (ii) the interplay between these factors during pre-initiation complex formation at the rDNA promoter in mammalian cells; and (iii) the cellular control of the Pol I transcription machinery.

scholarly journals Modifications of both selectivity factor and upstream binding factor contribute to poliovirus-mediated inhibition of RNA polymerase I transcription

2005 ◽  
Vol 86 (8) ◽  
pp. 2315-2322 ◽  
Author(s):  
Rajeev Banerjee ◽  
Mary K. Weidman ◽  
Sonia Navarro ◽  
Lucio Comai ◽  
Asim Dasgupta
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Selectivity Factor ◽  
Pol I ◽  
Binding Factor ◽  
Infected Cells ◽  
Upstream Binding Factor ◽  
Polymerase I

Soon after infection, poliovirus (PV) shuts off host-cell transcription, which is catalysed by all three cellular RNA polymerases. rRNA constitutes more than 50 % of all cellular RNA and is transcribed from rDNA by RNA polymerase I (pol I). Here, evidence has been provided suggesting that both pol I transcription factors, SL-1 (selectivity factor) and UBF (upstream binding factor), are modified and inactivated in PV-infected cells. The viral protease 3Cpro appeared to cleave the TATA-binding protein-associated factor 110 (TAF110), a subunit of the SL-1 complex, into four fragments in vitro. In vitro protease-cleavage assays using various mutants of TAF110 and purified 3Cpro indicated that the Q265G266 and Q805G806 sites were cleaved by 3Cpro. Both SL-1 and UBF were depleted in PV-infected cells and their disappearance correlated with pol I transcription inhibition. rRNA synthesis from a template containing a human pol I promoter demonstrated that both SL-1 and UBF were necessary to restore pol I transcription fully in PV-infected cell extracts. These results suggested that both SL-1 and UBF are transcriptionally inactivated in PV-infected HeLa cells.

scholarly journals A34.5, a nonessential component of yeast RNA polymerase I, cooperates with subunit A14 and DNA topoisomerase I to produce a functional rRNA synthesis machine.

1997 ◽  
Vol 17 (4) ◽  
pp. 1787-1795 ◽  
Author(s):  
O Gadal ◽  
S Mariotte-Labarre ◽  
S Chedin ◽  
E Quemeneur ◽  
C Carles ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Topoisomerase I ◽  
Synthetic Lethality ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Dna Topoisomerase I ◽  
Dna Topoisomerase ◽  
Pol Ii ◽  
Pol I ◽  
Polymerase I

A34.5, a phosphoprotein copurifying with RNA polymerase I (Pol I), lacks homology to any component of the Pol II or Pol III transcription complexes. Cells devoid of A34.5 hardly affect growth and rRNA synthesis and generate a catalytically active but structurally modified enzyme also lacking subunit A49 upon in vitro purification. Other Pol I-specific subunits (A49, A14, and A12.2) are nonessential for growth at 30 degrees C but are essential (A49 and A12.2) or helpful (A14) at 25 or 37 degrees C. Triple mutants without A34.5, A49, and A12.2 are viable, but inactivating any of these subunits together with A14 is lethal. Lethality is rescued by expressing pre-rRNA from a Pol II-specific promoter, demonstrating that these subunits are collectively essential but individually dispensable for rRNA synthesis. A14 and A34.5 single deletions affect the subunit composition of the purified enzyme in pleiotropic but nonoverlapping ways which, if accumulated in the double mutants, provide a structural explanation for their strict synthetic lethality. A34.5 (but not A14) becomes quasi-essential in strains lacking DNA topoisomerase I, suggesting a specific role of this subunit in helping Pol I to overcome the topological constraints imposed on ribosomal DNA by transcription.

scholarly journals RNA Polymerase I-Promoted HIS4Expression Yields Uncapped, Polyadenylated mRNA That Is Unstable and Inefficiently Translated in Saccharomyces cerevisiae

1998 ◽  
Vol 18 (2) ◽  
pp. 665-675 ◽  
Author(s):  
Hsiu-Jung Lo ◽  
Han-Kuei Huang ◽  
Thomas F. Donahue
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Steady State ◽  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Mutant Form ◽  
Wild Type ◽  
Pol I ◽  
Chromosome Iii ◽  
Polymerase I

ABSTRACT The HIS4 gene in Saccharomyces cerevisiaewas put under the transcriptional control of RNA polymerase I to determine the in vivo consequences on mRNA processing and gene expression. This gene, referred to as rhis4, was substituted for the normal HIS4 gene on chromosome III. Therhis4 gene transcribes two mRNAs, of which each initiates at the polymerase (pol) I transcription initiation site. One transcript, rhis4s, is similar in size to the wild-typeHIS4 mRNA. Its 3′ end maps to the HIS4 3′ noncoding region, and it is polyadenylated. The second transcript,rhis4l, is bicistronic. It encodes the HIS4coding region and a second open reading frame, YCL184, that is located downstream of the HIS4 gene and is predicted to be transcribed in the same direction as HIS4 on chromosome III. The 3′ end of rhis4l maps to the predicted 3′ end of the YCL184 gene and is also polyadenylated. Based on in vivo labeling experiments, the rhis4 gene appears to be more actively transcribed than the wild-type HIS4 gene despite the near equivalence of the steady-state levels of mRNAs produced from each gene. This finding indicated that rhis4mRNAs are rapidly degraded, presumably due to the lack of a cap structure at the 5′ end of the mRNA. Consistent with this interpretation, a mutant form of XRN1, which encodes a 5′-3′ exonuclease, was identified as an extragenic suppressor that increases the half-life of rhis4 mRNA, leading to a 10-fold increase in steady-state mRNA levels compared to the wild-typeHIS4 mRNA level. This increase is dependent on pol I transcription. Immunoprecipitation by anticap antiserum suggests that the majority of rhis4 mRNA produced is capless. In addition, we quantitated the level of His4 protein in a rhis4 xrn1Δ genetic background. This analysis indicates that capless mRNA is translated at less than 10% of the level of translation of capped HIS4 mRNA. Our data indicate that polyadenylation of mRNA in yeast occurs despite HIS4 being transcribed by RNA polymerase I, and the 5′ cap confers stability to mRNA and affords the ability of mRNA to be translated efficiently in vivo.

Cloning and characterization of SRP1, a suppressor of temperature-sensitive RNA polymerase I mutations, in Saccharomyces cerevisiae

1992 ◽  
Vol 12 (12) ◽  
pp. 5640-5651
Author(s):  
R Yano ◽  
M Oakes ◽  
M Yamaghishi ◽  
J A Dodd ◽  
M Nomura
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Rna Polymerase ◽  
Binding Domain ◽  
Rna Polymerase I ◽  
Zinc Binding ◽  
Temperature Sensitive ◽  
Pol I ◽  
Polymerase I ◽  
Zinc Binding Domain

The SRP1-1 mutation is an allele-specific dominant suppressor of temperature-sensitive mutations in the zinc-binding domain of the A190 subunit of Saccharomyces cerevisiae RNA polymerase I (Pol I). We found that it also suppresses temperature-sensitive mutations in the zinc-binding domain of the Pol I A135 subunit. This domain had been suggested to be in physical proximity to the A190 zinc-binding domain. We have cloned the SRP1 gene and determined its nucleotide sequence. The gene encodes a protein of 542 amino acids consisting of three domains: the central domain, which is composed of eight (degenerate) 42-amino-acid contiguous tandem repeats, and the surrounding N-terminal and C-terminal domains, both of which contain clusters of acidic and basic amino acids and are very hydrophilic. The mutational alteration (P219Q) responsible for the suppression was found to be in the central domain. Using antibody against the SRP1 protein, we have found that SRP1 is mainly localized at the periphery of the nucleus, apparently more concentrated in certain regions, as suggested by a punctate pattern in immunofluorescence microscopy. We suggest that SRP1 is a component of a larger macromolecular complex associated with the nuclear envelope and interacts with Pol I either directly or indirectly through other components in the structure containing SRP1.

scholarly journals A polymerase switch in the synthesis of rRNA in Saccharomyces cerevisiae.

1995 ◽  
Vol 15 (5) ◽  
pp. 2420-2428 ◽  
Author(s):  
H Conrad-Webb ◽  
R A Butow
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Dna ◽  
Sole Source ◽  
Rna Polymerase I ◽  
Yeast Cells ◽  
Dna Repeat ◽  
Polymerase I ◽  
Respiratory Deficient

Transcription of ribosomal DNA by RNA polymerase I is believed to be the sole source of the 25S, 18S, and 5.8S rRNAs in wild-type cells of Saccharomyces cerevisiae. Here we present evidence for a switch from RNA polymerase I to RNA polymerase II in the synthesis of a substantial fraction of those rRNAs in respiratory-deficient (petite) cells. The templates for the RNA polymerase II transcripts are largely, if not exclusively, episomal copies of ribosomal DNA arising from homologous recombination events within the ribosomal DNA repeat on chromosome XII. Ribosomal DNA contains a cryptic RNA polymerase II promoter that is activated in petites; it overlaps the RNA polymerase I promoter and produces a transcript equivalent to the 35S precursor rRNA made by RNA polymerase I. Yeast cells that lack RNA polymerase I activity, because of a disruption of the RPA135 gene that encodes subunit II of the enzyme, can survive by using the RNA polymerase II promoter in ribosomal DNA to direct the synthesis of the 35S rRNA precursor. This polymerase switch could provide cells with a mechanism to synthesize rRNA independent of the controls of RNA polymerase I transcription.

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