scholarly journals LAS1L interacts with the mammalian Rix1 complex to regulate ribosome biogenesis

2012 ◽  
Vol 23 (4) ◽  
pp. 716-728 ◽  
Author(s):  
Christopher D. Castle ◽  
Erica K. Cassimere ◽  
Catherine Denicourt
Keyword(s):  
Rna Polymerase ◽  
Nuclear Export ◽  
Ribosome Biogenesis ◽  
Ribosomal Subunit ◽  
Rna Polymerase I ◽  
G1 Arrest ◽  
Particle Assembly ◽  
Associated Proteins ◽  
Specific Protease ◽  
Polymerase I

The coordination of RNA polymerase I transcription with pre-rRNA processing, preribosomal particle assembly, and nuclear export is a finely tuned process requiring the concerted actions of a number of accessory factors. However, the exact functions of some of these proteins and how they assemble in subcomplexes remain poorly defined. LAS1L was first described as a nucleolar protein required for maturation of the 60S preribosomal subunit. In this paper, we demonstrate that LAS1L interacts with PELP1, TEX10, and WDR18, the mammalian homologues of the budding yeast Rix1 complex, along with NOL9 and SENP3, to form a novel nucleolar complex that cofractionates with the 60S preribosomal subunit. Depletion of LAS1L-associated proteins results in a p53-dependent G1 arrest and leads to defects in processing of the pre-rRNA internal transcribed spacer 2 region. We further show that the nucleolar localization of this complex requires active RNA polymerase I transcription and the small ubiquitin-like modifier–specific protease SENP3. Taken together, our data identify a novel mammalian complex required for 60S ribosomal subunit synthesis, providing further insight into the intricate, yet poorly described, process of ribosome biogenesis in higher eukaryotes.

scholarly journals Nucleocytoplasmic Traffic of CPEB1 and Accumulation in Crm1 Nucleolar Bodies

2009 ◽  
Vol 20 (1) ◽  
pp. 176-187 ◽  
Author(s):  
Michèle Ernoult-Lange ◽  
Ania Wilczynska ◽  
Maryannick Harper ◽  
Christelle Aigueperse ◽  
François Dautry ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Nuclear Export ◽  
Ribosome Biogenesis ◽  
Rna Polymerase I ◽  
Nuclear Bodies ◽  
Ribosome Assembly ◽  
Maternal Mrna ◽  
Ribosome Export ◽  
Polymerase I ◽  
Nuclear Export Receptor

The translational regulator CPEB1 plays a major role in the control of maternal mRNA in oocytes, as well as of subsynaptic mRNAs in neurons. Although mainly cytoplasmic, we found that CPEB1 protein is continuously shuttling between nucleus and cytoplasm. Its export is controlled by two redundant NES motifs dependent on the nuclear export receptor Crm1. In the nucleus, CPEB1 accumulates in a few foci most often associated with nucleoli. These foci are different from previously identified nuclear bodies. They contain Crm1 and were called Crm1 nucleolar bodies (CNoBs). CNoBs depend on RNA polymerase I activity, indicating a role in ribosome biogenesis. However, although they form in the nucleolus, they never migrate to the nuclear envelope, precluding a role as a mediator for ribosome export. They could rather constitute a platform providing factors for ribosome assembly or export. The behavior of CPEB1 in CNoBs raises the possibility that it is involved in ribosome biogenesis.

scholarly journals Drug-induced dispersal of transcribed rRNA genes and transcriptional products: immunolocalization and silver staining of different nucleolar components in rat cells treated with 5,6-dichloro-beta-D-ribofuranosylbenzimidazole.

1984 ◽  
Vol 99 (2) ◽  
pp. 672-679 ◽  
Author(s):  
U Scheer ◽  
B Hügle ◽  
R Hazan ◽  
K M Rose
Keyword(s):  
Rna Polymerase ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Ribosomal Subunit ◽  
Rna Polymerase I ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Linear Distribution ◽  
Nucleolar Material ◽  
Polymerase I

Upon incubation of cultured rat cells with the adenosine analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), nucleoli reversibly dissociate into their substructures, disperse throughout the nuclear interior, and form nucleolar "necklaces". We have used this experimental system, which does not inhibit transcription of the rRNA genes, to study by immunocytochemistry the distribution of active rRNA genes and their transcriptional products during nucleolar dispersal and recovery to normal morphology. Antibodies to RNA polymerase I allow detection of template-engaged polymerase, and monoclonal antibodies to a ribosomal protein (S1) of the small ribosomal subunit permit localization of nucleolar preribosomal particles. The results show that, under the action of DRB transcribed rRNA, genes spread throughout the nucleoplasm and finally appear in the form of several rows, each containing several (up to 30) granules positive for RNA polymerase I and argyrophilic proteins. Nucleolar material containing preribosomal particles also appears in granular structures spread over the nucleoplasm but its distribution is distinct from that of rRNA gene-containing granules. We conclude that, although transcriptional units and preribosomal particles are both redistributed in response to DRB, these entities retain their individuality as functionally defined subunits. We further propose that each RNA polymerase-positive granular unit represents a single transcription unit and that each continuous array of granules ("string of nucleolar beads") reflects the linear distribution of rRNA genes along a nucleolar organizer region. Based on the total number of polymerase I-positive granules we estimate that a minimum of 60 rRNA genes are active during interphase of DRB-treated rat cells.

scholarly journals Nuclear export of different classes of RNA is mediated by specific factors

1994 ◽  
Vol 124 (5) ◽  
pp. 627-635 ◽  
Author(s):  
A Jarmolowski ◽  
WC Boelens ◽  
E Izaurralde ◽  
IW Mattaj
Keyword(s):  
Rna Polymerase ◽  
Nuclear Export ◽  
Xenopus Oocytes ◽  
Common Factors ◽  
Rna Polymerase I ◽  
5S Rna ◽  
Small Nuclear Rnas ◽  
Nuclear Rna ◽  
Specific Factors ◽  
Polymerase I

Various classes of RNA are exported from the nucleus to the cytoplasm, including transcripts of RNA polymerase I (large ribosomal RNAs), II (U-rich small nuclear RNAs [U snRNAs], mRNAs), and III (tRNAs, 5S RNA). Here, evidence is presented that some steps in the export of various classes of nuclear RNA are mediated by specific rather than common factors. Using microinjection into Xenopus oocytes, it is shown that a tRNA, a U snRNA, and an mRNA competitively inhibit their own export at concentrations at which they have no effect on the export of heterologous RNAs. While the export of both U snRNAs and mRNAs is enhanced by their 7-methyl guanosine cap structures, factors recognizing this structure are found to be limiting in concentration only in the case of U snRNAs. In addition to the specific factors, evidence for steps in the export process that may be common to at least some classes of RNA are provided by experiments in which synthetic homopolymeric RNAs are used as inhibitors.

scholarly journals Nucleolar TFIIE plays a role in ribosomal biogenesis and performance

2020 ◽  
Author(s):  
Tamara Phan ◽  
Pallab Maity ◽  
Christina Ludwig ◽  
Lisa Streit ◽  
Jens Michaelis ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosome Biogenesis ◽  
Initiation Site ◽  
Rna Polymerase I ◽  
Ribosomal Biogenesis ◽  
Protein Coding ◽  
Degenerative Disorder ◽  
And Performance ◽  
Polymerase I

Ribosome biogenesis is a highly energy-demanding process in eukaryotes which requires the concerted action of all three RNA polymerases. In RNA polymerase II transcription, the general transcription factor TFIIH is recruited by TFIIE to the initiation site of protein-coding genes. Distinct mutations in TFIIH and TFIIE give rise to the degenerative disorder trichothiodystrophy (TTD). Here we uncovered an unexpected role of TFIIE in ribosomal RNA synthesis by RNA polymerase I. With high resolution microscopy we detected TFIIE in the nucleolus where TFIIE binds to actively transcribed rDNA. Mutations in TFIIE affects gene-occupancy of RNA polymerase I, rRNA maturation, ribosomal assembly and performance. In consequence, the elevated translational error rate with imbalanced protein synthesis and turnover results in an increase in heat-sensitive proteins. Collectively, mutations in TFIIE - due to impaired ribosomal biogenesis and translational accuracy - lead to a loss of protein homeostasis (proteostasis) which can partly explain the clinical phenotype in TTD.

scholarly journals Che-1/AATF binds to RNA polymerase I machinery and sustains ribosomal RNA gene transcription

2020 ◽  
Vol 48 (11) ◽  
pp. 5891-5906 ◽  
Author(s):  
Cristina Sorino ◽  
Valeria Catena ◽  
Tiziana Bruno ◽  
Francesca De Nicola ◽  
Stefano Scalera ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Rna Polymerase ◽  
Ribosomal Rna ◽  
Ribosome Biogenesis ◽  
Cellular Proliferation ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Rrna Gene ◽  
Response To Stress ◽  
Polymerase I

Abstract Originally identified as an RNA polymerase II interactor, Che-1/AATF (Che-1) has now been recognized as a multifunctional protein involved in cell-cycle regulation and cancer progression, as well as apoptosis inhibition and response to stress. This protein displays a peculiar nucleolar localization and it has recently been implicated in pre-rRNA processing and ribosome biogenesis. Here, we report the identification of a novel function of Che-1 in the regulation of ribosomal RNA (rRNA) synthesis, in both cancer and normal cells. We demonstrate that Che-1 interacts with RNA polymerase I and nucleolar upstream binding factor (UBF) and promotes RNA polymerase I-dependent transcription. Furthermore, this protein binds to the rRNA gene (rDNA) promoter and modulates its epigenetic state by contrasting the recruitment of HDAC1. Che-1 downregulation affects RNA polymerase I and UBF recruitment on rDNA and leads to reducing rDNA promoter activity and 47S pre-rRNA production. Interestingly, Che-1 depletion induces abnormal nucleolar morphology associated with re-distribution of nucleolar proteins. Finally, we show that upon DNA damage Che-1 re-localizes from rDNA to TP53 gene promoter to induce cell-cycle arrest. This previously uncharacterized function of Che-1 confirms the important role of this protein in the regulation of ribosome biogenesis, cellular proliferation and response to stress.

scholarly journals The dynamic assembly of distinct RNA polymerase I complexes modulates rDNA transcription

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Eva Torreira ◽  
Jaime Alegrio Louro ◽  
Irene Pazos ◽  
Noelia González-Polo ◽  
David Gil-Carton ◽  
...  
Keyword(s):  
Cell Growth ◽  
Rna Polymerase ◽  
Ribosome Biogenesis ◽  
Mutational Analysis ◽  
Rna Polymerase I ◽  
Initiation Factor ◽  
Rdna Transcription ◽  
Pol I ◽  
Polymerase I

Cell growth requires synthesis of ribosomal RNA by RNA polymerase I (Pol I). Binding of initiation factor Rrn3 activates Pol I, fostering recruitment to ribosomal DNA promoters. This fundamental process must be precisely regulated to satisfy cell needs at any time. We present in vivo evidence that, when growth is arrested by nutrient deprivation, cells induce rapid clearance of Pol I–Rrn3 complexes, followed by the assembly of inactive Pol I homodimers. This dual repressive mechanism reverts upon nutrient addition, thus restoring cell growth. Moreover, Pol I dimers also form after inhibition of either ribosome biogenesis or protein synthesis. Our mutational analysis, based on the electron cryomicroscopy structures of monomeric Pol I alone and in complex with Rrn3, underscores the central role of subunits A43 and A14 in the regulation of differential Pol I complexes assembly and subsequent promoter association.

scholarly journals The chemotherapeutic agent CX-5461 irreversibly blocks RNA polymerase I initiation and promoter release to cause nucleolar disruption, DNA damage and cell inviability

NAR Cancer ◽  
2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Jean-Clément Mars ◽  
Michel G Tremblay ◽  
Mélissa Valere ◽  
Dany S Sibai ◽  
Marianne Sabourin-Felix ◽  
...  
Keyword(s):  
Dna Damage ◽  
Rna Polymerase ◽  
Ribosomal Rna ◽  
Transcription Initiation ◽  
Ribosome Biogenesis ◽  
Chemotherapeutic Agent ◽  
Rna Polymerase I ◽  
Initiation Complex ◽  
Promoter Recruitment ◽  
Polymerase I

Abstract In the search for drugs to effectively treat cancer, the last 10 years have seen a resurgence of interest in targeting ribosome biogenesis. CX-5461 is a potential inhibitor of ribosomal RNA synthesis that is now showing promise in phase I trials as a chemotherapeutic agent for a range of malignancies. Here, we show that CX-5461 irreversibly inhibits ribosomal RNA transcription by arresting RNA polymerase I (RPI/Pol1/PolR1) in a transcription initiation complex. CX-5461 does not achieve this by preventing formation of the pre-initiation complex nor does it affect the promoter recruitment of the SL1 TBP complex or the HMGB-box upstream binding factor (UBF/UBTF). CX-5461 also does not prevent the subsequent recruitment of the initiation-competent RPI–Rrn3 complex. Rather, CX-5461 blocks promoter release of RPI–Rrn3, which remains irreversibly locked in the pre-initiation complex even after extensive drug removal. Unexpectedly, this results in an unproductive mode of RPI recruitment that correlates with the onset of nucleolar stress, inhibition of DNA replication, genome-wide DNA damage and cellular senescence. Our data demonstrate that the cytotoxicity of CX-5461 is at least in part the result of an irreversible inhibition of RPI transcription initiation and hence are of direct relevance to the design of improved strategies of chemotherapy.

scholarly journals Ribosomal RNA Transcription Regulation in Breast Cancer

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 502
Author(s):  
Cecelia M. Harold ◽  
Amber F. Buhagiar ◽  
Yan Cheng ◽  
Susan J. Baserga
Keyword(s):  
Breast Cancer ◽  
Rna Polymerase ◽  
Ribosomal Rna ◽  
Ribosome Biogenesis ◽  
Rna Polymerase I ◽  
Cancer Therapies ◽  
Rdna Transcription ◽  
Global Protein Synthesis ◽  
Novel Drugs ◽  
Polymerase I

Ribosome biogenesis is a complex process that is responsible for the formation of ribosomes and ultimately global protein synthesis. The first step in this process is the synthesis of the ribosomal RNA in the nucleolus, transcribed by RNA Polymerase I. Historically, abnormal nucleolar structure is indicative of poor cancer prognoses. In recent years, it has been shown that ribosome biogenesis, and rDNA transcription in particular, is dysregulated in cancer cells. Coupled with advancements in screening technology that allowed for the discovery of novel drugs targeting RNA Polymerase I, this transcriptional machinery is an increasingly viable target for cancer therapies. In this review, we discuss ribosome biogenesis in breast cancer and the different cellular pathways involved. Moreover, we discuss current therapeutics that have been found to affect rDNA transcription and more novel drugs that target rDNA transcription machinery as a promising avenue for breast cancer treatment.

scholarly journals Increased numbers of nucleoli in a genome-wide RNAi screen reveal proteins that link the cell cycle to RNA polymerase I transcription

2021 ◽  
Vol 32 (9) ◽  
pp. 956-973 ◽  
Author(s):  
Lisa M. Ogawa ◽  
Amber F. Buhagiar ◽  
Laura Abriola ◽  
Bryan A. Leland ◽  
Yulia V. Surovtseva ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Rna Polymerase ◽  
Ribosome Biogenesis ◽  
Rna Polymerase I ◽  
Wide Field ◽  
Genome Wide ◽  
A Genome ◽  
Nucleolar Number ◽  
Polymerase I ◽  
Cycle Regulation

The nucleolus is a dynamic nuclear condensate and site of ribosome biogenesis. Using wide-field fluorescence microscopy, we screened for proteins that when depleted cause an increase in nucleolar number. Our results uncovered an unexpected subset of proteins that link the nucleolus, cell cycle regulation, and RNA polymerase I transcription.

scholarly journals Targeting the RNA Polymerase I Transcription for Cancer Therapy Comes of Age

Cells ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 266 ◽  
Author(s):  
Rita Ferreira ◽  
John S. Schneekloth ◽  
Konstantin I. Panov ◽  
Katherine M. Hannan ◽  
Ross D. Hannan
Keyword(s):  
Rna Polymerase ◽  
Cancer Progression ◽  
Ribosome Biogenesis ◽  
Therapeutic Potential ◽  
Cancer Therapeutics ◽  
Active Role ◽  
Rna Polymerase I ◽  
Cancer Etiology ◽  
Pol I ◽  
Polymerase I

Transcription of the ribosomal RNA genes (rDNA) that encode the three largest ribosomal RNAs (rRNA), is mediated by RNA Polymerase I (Pol I) and is a key regulatory step for ribosomal biogenesis. Although it has been reported over a century ago that the number and size of nucleoli, the site of ribosome biogenesis, are increased in cancer cells, the significance of this observation for cancer etiology was not understood. The realization that the increase in rRNA expression has an active role in cancer progression, not only through increased protein synthesis and thus proliferative capacity but also through control of cellular check points and chromatin structure, has opened up new therapeutic avenues for the treatment of cancer through direct targeting of Pol I transcription. In this review, we discuss the rational of targeting Pol I transcription for the treatment of cancer; review the current cancer therapeutics that target Pol I transcription and discuss the development of novel Pol I-specific inhibitors, their therapeutic potential, challenges and future prospects.

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