scholarly journals Human rDNA and Cancer

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3452
Author(s):  
Evgeny Smirnov ◽  
Nikola Chmúrčiaková ◽  
Dušan Cmarko
Keyword(s):  
Fragile Site ◽  
Intergenic Spacer ◽  
Rdna Locus ◽  
Stress Reactions ◽  
Rdna Unit ◽  
Functional Regions ◽  
Pol I ◽  
Non Coding Rnas ◽  
Cancer Multiple ◽  
Polymerase I

In human cells, each rDNA unit consists of the ~13 kb long ribosomal part and ~30 kb long intergenic spacer (IGS). The ribosomal part, transcribed by RNA polymerase I (pol I), includes genes coding for 18S, 5.8S, and 28S RNAs of the ribosomal particles, as well as their four transcribed spacers. Being highly repetitive, intensively transcribed, and abundantly methylated, rDNA is a very fragile site of the genome, with high risk of instability leading to cancer. Multiple small mutations, considerable expansion or contraction of the rDNA locus, and abnormally enhanced pol I transcription are usual symptoms of transformation. Recently it was found that both IGS and the ribosomal part of the locus contain many functional/potentially functional regions producing non-coding RNAs, which participate in the pol I activity regulation, stress reactions, and development of the malignant phenotype. Thus, there are solid reasons to believe that rDNA locus plays crucial role in carcinogenesis. In this review we discuss the data concerning the human rDNA and its closely associated factors as both targets and drivers of the pathways essential for carcinogenesis. We also examine whether variability in the structure of the locus may be blamed for the malignant transformation. Additionally, we consider the prospects of therapy focused on the activity of rDNA.

scholarly journals RNA Polymerase I Transcription Silences Noncoding RNAs at the Ribosomal DNA Locus in Saccharomyces cerevisiae

2009 ◽  
Vol 9 (2) ◽  
pp. 325-335 ◽  
Author(s):  
Elisa Cesarini ◽  
Francesca Romana Mariotti ◽  
Francesco Cioci ◽  
Giorgio Camilloni
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Rna Polymerase Iii ◽  
Noncoding Rnas ◽  
Rdna Locus ◽  
Rna Polymerase I ◽  
Pol Ii ◽  
Pol I ◽  
Polymerase I

ABSTRACT In Saccharomyces cerevisiae the repeated units of the ribosomal locus, transcribed by RNA polymerase I (Pol I), are interrupted by nontranscribed spacers (NTSs). These NTS regions are transcribed by RNA polymerase III to synthesize 5S RNA and by RNA polymerase II (Pol II) to synthesize, at low levels, noncoding RNAs (ncRNAs). While transcription of both RNA polymerase I and III is highly characterized, at the ribosomal DNA (rDNA) locus only a few studies have been performed on Pol II, whose repression correlates with the SIR2-dependent silencing. The involvement of both chromatin organization and Pol I transcription has been proposed, and peculiar chromatin structures might justify “ribosomal” Pol II silencing. Reporter genes inserted within the rDNA units have been employed for these studies. We studied, in the natural context, yeast mutants differing in Pol I transcription in order to find whether correlations exist between Pol I transcription and Pol II ncRNA production. Here, we demonstrate that silencing at the rDNA locus represses ncRNAs with a strength inversely proportional to Pol I transcription. Moreover, localized regions of histone hyperacetylation appear in cryptic promoter elements when Pol II is active and in the coding region when Pol I is functional; in addition, DNA topoisomerase I site-specific activity follows RNA polymerase I transcription. The repression of ncRNAs at the rDNA locus, in response to RNA polymerase I transcription, could represent a physiological circuit control whose mechanism involves modification of histone acetylation.

scholarly journals The Ribosomal Gene Loci—The Power behind the Throne

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 763
Author(s):  
Konstantin I. Panov ◽  
Katherine Hannan ◽  
Ross D. Hannan ◽  
Nadine Hein
Keyword(s):  
Genome Stability ◽  
Cell Cycle Progression ◽  
Global Gene Expression ◽  
Cell Types ◽  
Ribosomal Gene ◽  
Cellular Growth ◽  
Rrna Genes ◽  
Dynamic Regulation ◽  
Pol I ◽  
Polymerase I

Nucleoli form around actively transcribed ribosomal RNA (rRNA) genes (rDNA), and the morphology and location of nucleolus-associated genomic domains (NADs) are linked to the RNA Polymerase I (Pol I) transcription status. The number of rDNA repeats (and the proportion of actively transcribed rRNA genes) is variable between cell types, individuals and disease state. Substantial changes in nucleolar morphology and size accompanied by concomitant changes in the Pol I transcription rate have long been documented during normal cell cycle progression, development and malignant transformation. This demonstrates how dynamic the nucleolar structure can be. Here, we will discuss how the structure of the rDNA loci, the nucleolus and the rate of Pol I transcription are important for dynamic regulation of global gene expression and genome stability, e.g., through the modulation of long-range genomic interactions with the suppressive NAD environment. These observations support an emerging paradigm whereby the rDNA repeats and the nucleolus play a key regulatory role in cellular homeostasis during normal development as well as disease, independent of their role in determining ribosome capacity and cellular growth rates.

scholarly journals The Splicing ATPase Prp43p Is a Component of Multiple Preribosomal Particles

2005 ◽  
Vol 25 (21) ◽  
pp. 9269-9282 ◽  
Author(s):  
Simon Lebaron ◽  
Carine Froment ◽  
Micheline Fromont-Racine ◽  
Jean-Christophe Rain ◽  
Bernard Monsarrat ◽  
...  
Keyword(s):  
Affinity Purification ◽  
Rna Polymerase I ◽  
Rrna Processing ◽  
Rrna Transcription ◽  
Pol I ◽  
Final Maturation ◽  
Steady State Levels ◽  
Splicing Defects ◽  
Polymerase I ◽  
Two Hybrid

ABSTRACT Prp43p is a putative helicase of the DEAH family which is required for the release of the lariat intron from the spliceosome. Prp43p could also play a role in ribosome synthesis, since it accumulates in the nucleolus. Consistent with this hypothesis, we find that depletion of Prp43p leads to accumulation of 35S pre-rRNA and strongly reduces levels of all downstream pre-rRNA processing intermediates. As a result, the steady-state levels of mature rRNAs are greatly diminished following Prp43p depletion. We present data arguing that such effects are unlikely to be solely due to splicing defects. Moreover, we demonstrate by a combination of a comprehensive two-hybrid screen, tandem-affinity purification followed by mass spectrometry, and Northern analyses that Prp43p is associated with 90S, pre-60S, and pre-40S ribosomal particles. Prp43p seems preferentially associated with Pfa1p, a novel specific component of pre-40S ribosomal particles. In addition, Prp43p interacts with components of the RNA polymerase I (Pol I) transcription machinery and with mature 18S and 25S rRNAs. Hence, Prp43p might be delivered to nascent 90S ribosomal particles during pre-rRNA transcription and remain associated with preribosomal particles until their final maturation steps in the cytoplasm. Our data also suggest that the ATPase activity of Prp43p is required for early steps of pre-rRNA processing and normal accumulation of mature rRNAs.

scholarly journals Production of Infectious Hepatitis C Virus by Using RNA Polymerase I-Mediated Transcription

2010 ◽  
Vol 84 (11) ◽  
pp. 5824-5835 ◽  
Author(s):  
Takahiro Masaki ◽  
Ryosuke Suzuki ◽  
Mohsan Saeed ◽  
Ken-ichi Mori ◽  
Mami Matsuda ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Cell Line ◽  
Viral Genome ◽  
Rna Polymerase I ◽  
Virion Assembly ◽  
Pol I ◽  
Positive Strand Rna ◽  
Polymerase I

ABSTRACT In this study, we used an RNA polymerase I (Pol I) transcription system for development of a reverse genetics protocol to produce hepatitis C virus (HCV), which is an uncapped positive-strand RNA virus. Transfection with a plasmid harboring HCV JFH-1 full-length cDNA flanked by a Pol I promoter and Pol I terminator yielded an unspliced RNA with no additional sequences at either end, resulting in efficient RNA replication within the cytoplasm and subsequent production of infectious virions. Using this technology, we developed a simple replicon trans-packaging system, in which transient transfection of two plasmids enables examination of viral genome replication and virion assembly as two separate steps. In addition, we established a stable cell line that constitutively produces HCV with a low mutation frequency of the viral genome. The effects of inhibitors of N-linked glycosylation on HCV production were evaluated using this cell line, and the results suggest that certain step(s), such as virion assembly, intracellular trafficking, and secretion, are potentially up- and downregulated according to modifications of HCV envelope protein glycans. This Pol I-based HCV expression system will be beneficial for a high-throughput antiviral screening and vaccine discovery programs.

scholarly journals RNA polymerase I (Pol I) passage through nucleosomes depends on Pol I subunits binding its lobe structure

2020 ◽  
Vol 295 (15) ◽  
pp. 4782-4795 ◽  
Author(s):  
Philipp E. Merkl ◽  
Michael Pilsl ◽  
Tobias Fremter ◽  
Katrin Schwank ◽  
Christoph Engel ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Dna Templates ◽  
Pol Ii ◽  
Naked Dna ◽  
Pol I ◽  
Intrinsic Capacity ◽  
Pol Iii ◽  
Polymerase I

RNA polymerase I (Pol I) is a highly efficient enzyme specialized in synthesizing most ribosomal RNAs. After nucleosome deposition at each round of rDNA replication, the Pol I transcription machinery has to deal with nucleosomal barriers. It has been suggested that Pol I–associated factors facilitate chromatin transcription, but it is unknown whether Pol I has an intrinsic capacity to transcribe through nucleosomes. Here, we used in vitro transcription assays to study purified WT and mutant Pol I variants from the yeast Saccharomyces cerevisiae and compare their abilities to pass a nucleosomal barrier with those of yeast Pol II and Pol III. Under identical conditions, purified Pol I and Pol III, but not Pol II, could transcribe nucleosomal templates. Pol I mutants lacking either the heterodimeric subunit Rpa34.5/Rpa49 or the C-terminal part of the specific subunit Rpa12.2 showed a lower processivity on naked DNA templates, which was even more reduced in the presence of a nucleosome. Our findings suggest that the lobe-binding subunits Rpa34.5/Rpa49 and Rpa12.2 facilitate passage through nucleosomes, suggesting possible cooperation among these subunits. We discuss the contribution of Pol I–specific subunit domains to efficient Pol I passage through nucleosomes in the context of transcription rate and processivity.

scholarly journals Mutational Analysis of the Structure and Localization of the Nucleolus in the Yeast Saccharomyces cerevisiae

1998 ◽  
Vol 143 (1) ◽  
pp. 23-34 ◽  
Author(s):  
M. Oakes ◽  
J.P. Aris ◽  
J.S. Brockenbrough ◽  
H. Wai ◽  
L. Vu ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Mutational Analysis ◽  
Fusion Gene ◽  
Nuclear Periphery ◽  
Rdna Locus ◽  
Coding Region ◽  
Yeast Saccharomyces Cerevisiae ◽  
Pol I ◽  
Rdna Expression

The nucleolus in Saccharomyces cerevisiae is a crescent-shaped structure that makes extensive contact with the nuclear envelope. In different chromosomal rDNA deletion mutants that we have analyzed, the nucleolus is not organized into a crescent structure, as determined by immunofluorescence microscopy, fluorescence in situ hybridization, and electron microscopy. A strain carrying a plasmid with a single rDNA repeat transcribed by RNA polymerase I (Pol I) contained a fragmented nucleolus distributed throughout the nucleus, primarily localized at the nuclear periphery. A strain carrying a plasmid with the 35S rRNA coding region fused to the GAL7 promoter and transcribed by Pol II contained a rounded nucleolus that often lacked extensive contact with the nuclear envelope. Ultrastructurally distinct domains were observed within the round nucleolus. A similar rounded nucleolar morphology was also observed in strains carrying the Pol I plasmid in combination with mutations that affect Pol I function. In a Pol I–defective mutant strain that carried copies of the GAL7-35S rDNA fusion gene integrated into the chromosomal rDNA locus, the nucleolus exhibited a round morphology, but was more closely associated with the nuclear envelope in the form of a bulge. Thus, both the organization of the rDNA genes and the type of polymerase involved in rDNA expression strongly influence the organization and localization of the nucleolus.

scholarly journals Dichotomous Impact of Myc on rRNA Gene Activation and Silencing in B Cell Lymphomagenesis

Cancers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 3009
Author(s):  
Gaurav Joshi ◽  
Alexander Otto Eberhardt ◽  
Lisa Lange ◽  
René Winkler ◽  
Steve Hoffmann ◽  
...  
Keyword(s):  
B Cell ◽  
Gene Activation ◽  
Cpg Methylation ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Rdna Transcription ◽  
Highly Active ◽  
Pol I ◽  
Polymerase I ◽  
Transcriptional Output

A major transcriptional output of cells is ribosomal RNA (rRNA), synthesized by RNA polymerase I (Pol I) from multicopy rRNA genes (rDNA). Constitutive silencing of an rDNA fraction by promoter CpG methylation contributes to the stabilization of these otherwise highly active loci. In cancers driven by the oncoprotein Myc, excessive Myc directly stimulates rDNA transcription. However, it is not clear when during carcinogenesis this mechanism emerges, and how Myc-driven rDNA activation affects epigenetic silencing. Here, we have used the Eµ-Myc mouse model to investigate rDNA transcription and epigenetic regulation in Myc-driven B cell lymphomagenesis. We have developed a refined cytometric strategy to isolate B cells from the tumor initiation, promotion, and progression phases, and found a substantial increase of both Myc and rRNA gene expression only in established lymphoma. Surprisingly, promoter CpG methylation and the machinery for rDNA silencing were also strongly up-regulated in the tumor progression state. The data indicate a dichotomous role of oncogenic Myc in rDNA regulation, boosting transcription as well as reinforcing repression of silent repeats, which may provide a novel angle on perturbing Myc function in cancer cells.

scholarly journals Molecular Topology of RNA Polymerase I Upstream Activation Factor

2020 ◽  
Vol 40 (13) ◽  
Author(s):  
Bruce A. Knutson ◽  
Marissa L. Smith ◽  
Alana E. Belkevich ◽  
Aula M. Fakhouri
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Dual Function ◽  
Molecular Topology ◽  
Content Type ◽  
Histone Fold ◽  
Topological Features ◽  
Pol I ◽  
Activation Factor ◽  
Polymerase I

ABSTRACT Upstream activation factor (UAF) is a multifunctional transcription factor in Saccharomyces cerevisiae that plays dual roles in activating RNA polymerase I (Pol I) transcription and repression of Pol II. For Pol I, UAF binds to a specific upstream element in the ribosomal DNA (rDNA) promoter and interacts with two other Pol I initiation factors, the TATA-binding protein (TBP) and core factor (CF). We used an integrated combination of chemical cross-linking mass spectrometry (CXMS), molecular genetics, protein biochemistry, and structural modeling to understand the topological framework responsible for UAF complex formation. Here, we report the molecular topology of the UAF complex, describe new structural and functional domains that play roles in UAF complex integrity, assembly, and biological function, and provide roles for previously identified UAF domains that include the Rrn5 SANT and histone fold domains. We highlight the role of new domains in Uaf30 that include an N-terminal winged helix domain and a disordered tethering domain as well as a BORCS6-like domain found in Rrn9. Together, our results reveal a unique network of topological features that coalesce around a histone tetramer-like core to form the dual-function UAF complex.

scholarly journals A system for the analysis of yeast ribosomal DNA mutations.

1989 ◽  
Vol 9 (2) ◽  
pp. 551-559 ◽  
Author(s):  
W Musters ◽  
J Venema ◽  
G van der Linden ◽  
H van Heerikhuizen ◽  
J Klootwijk ◽  
...  
Keyword(s):  
Ribosomal Dna ◽  
Rdna Locus ◽  
Rrna Gene ◽  
Yeast Saccharomyces Cerevisiae ◽  
Yeast Plasmid ◽  
Rdna Unit ◽  
Dna Mutations ◽  
26S Rrna ◽  
And Function ◽  
Domain I

To develop a system for the analysis of eucaryotic ribosomal DNA (rDNA) mutations, we cloned a complete, transcriptionally active rDNA unit from the yeast Saccharomyces cerevisiae on a centromere-containing yeast plasmid. To distinguish the plasmid-derived ribosomal transcripts from those encoded by the rDNA locus, we inserted a tag of 18 base pairs within the first expansion segment of domain I of the 26S rRNA gene. We demonstrate that this insertion behaves as a neutral mutation since tagged 26S rRNA is normally processed and assembled into functional ribosomal subunits. This system allows us to study the effect of subsequent mutations within the tagged rDNA unit on the biosynthesis and function of the rRNA. As a first application, we wanted to ascertain whether the assembly of a 60S subunit is dependent on the presence in cis of an intact 17S rRNA gene. We found that a deletion of two-thirds of the 17S rRNA gene has no effect on the accumulation of active 60S subunits derived from the same operon. On the other hand, deletions within the second domain of the 26S rRNA gene completely abolished the accumulation of mature 26S rRNA.

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