scholarly journals Rapamycin Induces the G0 Program of Transcriptional Repression in Yeast by Interfering with the TOR Signaling Pathway

1998 ◽  
Vol 18 (8) ◽  
pp. 4463-4470 ◽  
Author(s):  
Dean Zaragoza ◽  
Ataollah Ghavidel ◽  
Joseph Heitman ◽  
Michael C. Schultz
Keyword(s):  
Signaling Pathway ◽  
Transcriptional Repression ◽  
Transcription Initiation ◽  
Cellular Proliferation ◽  
Yeast Cells ◽  
Initiation Factor ◽  
Independent Effect ◽  
Tor Signaling ◽  
Pol I ◽  
Pol Iii

ABSTRACT The macrolide antibiotic rapamycin inhibits cellular proliferation by interfering with the highly conserved TOR (for target of rapamycin) signaling pathway. Growth arrest of budding yeast cells treated with rapamycin is followed by the program of molecular events that characterizes entry into G0 (stationary phase), including the induction of polymerase (Pol) II genes typically expressed only in G0. Normally, progression into G0 is characterized by transcriptional repression of the Pol I and III genes. Here, we show that rapamycin treatment also causes the transcriptional repression of Pol I and III genes. The down-regulation of Pol III transcription is TOR dependent. While it coincides with translational repression by rapamycin, transcriptional repression is due in part to a translation-independent effect that is evident in extracts from a conditional tor2 mutant. Biochemical experiments reveal that RNA Pol III and probably transcription initiation factor TFIIIB are targets of repression by rapamycin. In view of previous evidence that TFIIIB and Pol III are inhibited when protein phosphatase 2A (PP2A) function is impaired, and that PP2A is a component of the TOR pathway, our results suggest that TOR signaling regulates Pol I and Pol III transcription in response to nutrient growth signals.

scholarly journals The BN51 protein is a polymerase (Pol)-specific subunit of RNA Pol III which reveals a link between Pol III transcription and pre-rRNA processing.

1995 ◽  
Vol 15 (1) ◽  
pp. 94-101 ◽  
Author(s):  
A J Jackson ◽  
M Ittmann ◽  
B F Pugh
Keyword(s):  
Yeast Cells ◽  
Temperature Sensitive ◽  
28S Rrna ◽  
Nonpermissive Temperature ◽  
Biochemical Evidence ◽  
Pol I ◽  
Nuclear Extracts ◽  
A Subunit ◽  
Pol Iii ◽  
Mammalian System

The three eukaryotic nuclear RNA polymerase (Pol) contain common and unique subunits. Cloning of the unique Pol III subunit genes in yeast cells has revealed a potential homolog in the mammalian system, the BN51 gene. The human BN51 gene was originally isolated as a suppressor of a temperature-sensitive cell cycle mutant of BHK cells (tsBN51). Although tsBN51 cells have a marked decrease in RNA Pol III activity at the nonpermissive temperature, direct biochemical evidence for the BN51 protein being a human Pol III subunit was lacking. Using antibodies directed against the BN51 protein, we show the following: (i) the BN51 protein copurifies with Pol III activity, (ii) Pol III activity can be specifically immunoprecipitated from HeLa nuclear extracts, and (iii) the immunopurified BN51 complex is active in restoring both nonspecific and promoter-specific Pol III activity. Our findings provide direct biochemical evidence for BN51 being a Pol III-specific subunit. Despite the fact that BN51 is not a subunit of Pol I, the production of mature Pol I transcripts is inhibited in tsBN51 cells at the nonpermissive temperature. tsBN51 cells appear defective in processing the 32S precursor rRNA into mature 5.8S and 28S rRNA at the nonpermissive temperature. We surmise that ribosome assembly has halted because of the loss of Pol III transcripts. Thus, there is regulation of the synthesis of mature Pol I transcripts by a posttranscriptional mechanism based on the availability of Pol III transcripts.

scholarly journals Spt6 Is Essential for rRNA Synthesis by RNA Polymerase I

2015 ◽  
Vol 35 (13) ◽  
pp. 2321-2331 ◽  
Author(s):  
Krysta L. Engel ◽  
Sarah L. French ◽  
Olga V. Viktorovskaya ◽  
Ann L. Beyer ◽  
David A. Schneider
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Initiation Factor ◽  
Rrna Synthesis ◽  
Temperature Sensitive ◽  
Protein Levels ◽  
Pol I ◽  
Low Levels ◽  
Sensitive Allele ◽  
Polymerase I

Spt6 (suppressor ofTy6) has many roles in transcription initiation and elongation by RNA polymerase (Pol) II. These effects are mediated through interactions with histones, transcription factors, and the RNA polymerase. Two lines of evidence suggest that Spt6 also plays a role in rRNA synthesis. First, Spt6 physically associates with a Pol I subunit (Rpa43). Second, Spt6 interacts physically and genetically with Spt4/5, which directly affects Pol I transcription. Utilizing a temperature-sensitive allele,spt6-1004, we show that Spt6 is essential for Pol I occupancy of the ribosomal DNA (rDNA) and rRNA synthesis. Our data demonstrate that protein levels of an essential Pol I initiation factor, Rrn3, are reduced when Spt6 is inactivated, leading to low levels of Pol I-Rrn3 complex. Overexpression ofRRN3rescues Pol I-Rrn3 complex formation; however, rRNA synthesis is not restored. These data suggest that Spt6 is involved in either recruiting the Pol I-Rrn3 complex to the rDNA or stabilizing the preinitiation complex. The findings presented here identify an unexpected, essential role for Spt6 in synthesis of rRNA.

scholarly journals Widespread Use of TATA Elements in the Core Promoters for RNA Polymerases III, II, and I in Fission Yeast

2001 ◽  
Vol 21 (20) ◽  
pp. 6870-6881 ◽  
Author(s):  
Mitsuhiro Hamada ◽  
Ying Huang ◽  
Todd M. Lowe ◽  
Richard J. Maraia
Keyword(s):  
Fission Yeast ◽  
Regulatory Elements ◽  
5S Rrna ◽  
Initiation Factor ◽  
Rrna Genes ◽  
Rrna Synthesis ◽  
Core Promoters ◽  
The Core ◽  
Pol I ◽  
Pol Iii

ABSTRACT In addition to directing transcription initiation, core promoters integrate input from distal regulatory elements. Except for rare exceptions, it has been generally found that eukaryotic tRNA and rRNA genes do not contain TATA promoter elements and instead use protein-protein interactions to bring the TATA-binding protein (TBP), to the core promoter. Genomewide analysis revealed TATA elements in the core promoters of tRNA and 5S rRNA (Pol III), U1 to U5 snRNA (Pol II), and 37S rRNA (Pol I) genes in Schizosaccharomyces pombe. Using tRNA-dependent suppression and other in vivo assays, as well as in vitro transcription, we demonstrated an obligatory requirement for upstream TATA elements for tRNA and 5S rRNA expression in S. pombe. The Pol III initiation factor Brf is found in complexes with TFIIIC and Pol III in S. pombe, while TBP is not, consistent with independent recruitment of TBP by TATA. Template commitment assays are consistent with this and confirm that the mechanisms of transcription complex assembly and initiation by Pol III in S. pombe differ substantially from those in other model organisms. The results were extended to large-rRNA synthesis, as mutation of the TATA element in the Pol I promoter also abolishes rRNA expression in fission yeast. A survey of other organisms' genomes reveals that a substantial number of eukaryotes may use widespread TATAs for transcription. These results indicate the presence of TATA-unified transcription systems in contemporary eukaryotes and provide insight into the residual need for TBP by all three Pols in other eukaryotes despite a lack of TATA elements in their promoters.

scholarly journals RNA Polymerase III Subunit Mutations in Genetic Diseases

2021 ◽  
Vol 8 ◽  
Author(s):  
Elisabeth Lata ◽  
Karine Choquet ◽  
Francis Sagliocco ◽  
Bernard Brais ◽  
Geneviève Bernard ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Rna Polymerase Iii ◽  
Initiation Factor ◽  
Varicella Zoster ◽  
Vital Functions ◽  
Genes Encoding ◽  
Pol Iii

RNA polymerase (Pol) III transcribes small untranslated RNAs such as 5S ribosomal RNA, transfer RNAs, and U6 small nuclear RNA. Because of the functions of these RNAs, Pol III transcription is best known for its essential contribution to RNA maturation and translation. Surprisingly, it was discovered in the last decade that various inherited mutations in genes encoding nine distinct subunits of Pol III cause tissue-specific diseases rather than a general failure of all vital functions. Mutations in the POLR3A, POLR3C, POLR3E and POLR3F subunits are associated with susceptibility to varicella zoster virus-induced encephalitis and pneumonitis. In addition, an ever-increasing number of distinct mutations in the POLR3A, POLR3B, POLR1C and POLR3K subunits cause a spectrum of neurodegenerative diseases, which includes most notably hypomyelinating leukodystrophy. Furthermore, other rare diseases are also associated with mutations in genes encoding subunits of Pol III (POLR3H, POLR3GL) and the BRF1 component of the TFIIIB transcription initiation factor. Although the causal relationship between these mutations and disease development is widely accepted, the exact molecular mechanisms underlying disease pathogenesis remain enigmatic. Here, we review the current knowledge on the functional impact of specific mutations, possible Pol III-related disease-causing mechanisms, and animal models that may help to better understand the links between Pol III mutations and disease.

scholarly journals A post-recruitment function for the RNA polymerase III transcription–initiation factor IIIB

1998 ◽  
Vol 95 (16) ◽  
pp. 9196-9201 ◽  
Author(s):  
George A. Kassavetis ◽  
Ashok Kumar ◽  
Garth A. Letts ◽  
E. Peter Geiduschek
Keyword(s):  
Transcription Factor ◽  
Rna Polymerase ◽  
Transcription Initiation ◽  
Transcriptional Start Site ◽  
Rna Polymerase Iii ◽  
Active Role ◽  
Normal Function ◽  
Initiation Factor ◽  
Transcriptional Initiation ◽  
Pol Iii

Transcription factor (TF) IIIB, which directs RNA polymerase (pol) III to its promoters, is made up of three components: the TATA box-binding protein, the TFIIB-related Brf, and the pol III-specific B′′. Certain mutations in Saccharomyces cerevisiae Brf and B′′ retain TFIIIB transcription factor activity with supercoiled DNA but are inactive with linear duplex DNA. Further analysis shows that these inactive TFIIIB–DNA complexes bind pol III and position it appropriately over the transcriptional start site but do not form DNA strand-separated open promoter complexes. It is proposed that the normal function of TFIIIB combines pol III recruitment with an active role in a subsequent step of transcriptional initiation leading to promoter opening.

Nucleolar biogenesis: the first small steps

2005 ◽  
Vol 33 (6) ◽  
pp. 1441-1443 ◽  
Author(s):  
J.-L. Prieto ◽  
B. McStay
Keyword(s):  
Transcription Initiation ◽  
Nucleolar Organizer ◽  
Gene Clusters ◽  
Initial Step ◽  
Ribosomal Gene ◽  
Initiation Factor ◽  
Nucleolar Organizer Regions ◽  
Pol I ◽  
Late Telophase ◽  
Polymerase I

The nucleolus is the site of rRNA transcription, pre-rRNA processing and ribosome subunit assembly. The nucleolus assembles around clusters of ribosomal gene repeats during late telophase, persists throughout interphase and then disassembles as cells enter mitosis. The initial step in nucleolar formation is ribosomal gene transcription, which is mediated by Pol I (RNA polymerase I) and its associated transcription factors: UBF (upstream-binding factor), SL1 (selectivity factor) and TIF-IA (transcription initiation factor IA)/Rrn3. Ribosomal gene clusters, termed NORs (nucleolar organizer regions), are found on each of the five human acrocentric chromosomes. Though transcription is repressed during metaphase, NORs that were active in the previous interphase form prominent cytogenetic features, namely secondary constrictions. The main defining characteristic of these constrictions is under-condensation in comparison with the rest of the chromosome. Extensive binding of UBF over the ribosomal gene repeat is responsible for the formation of this chromosomal feature. During interphase, the majority of the Pol I transcription machinery, though present in nucleoli, is not actively engaged in transcription. Interaction with UBF bound across the gene repeat provides an explanation for how this non-engaged Pol I machinery is sequestered by nucleoli.

scholarly journals Eukaryotic Initiation Factor-2, Gamma Subunit, Suppresses Proliferation and Regulates the Cell Cycle via the MAPK/ERK Signaling Pathway in Acute Myeloid Leukemia

2021 ◽  
Author(s):  
Jielun Lu ◽  
SHUYI CHEN ◽  
HUO TAN ◽  
ZHENQIAN HUANG ◽  
BO LI ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Acute Myeloid Leukemia ◽  
Signaling Pathway ◽  
Myeloid Leukemia ◽  
Cellular Proliferation ◽  
Initiation Factor ◽  
Erk Signaling ◽  
Phase Cell ◽  
Initiation Factor 2 ◽  
Acute Myeloid

Abstract Purpose The expression of eukaryotic translation initiation factor 2 subunit 3 (EIF2S3) in patients with non-small cell lung and colorectal cancer is lower than that in healthy individuals. However, the functions of EIF2S3 remain unclear, and its study in leukemia has not been reported. The article aims to explore the role of EIF2S3 in AML (acute myeloid leukemia) and its underlying mechanism. Methods Reverse transcription-quantitative PCR was performed to evaluate the expression levels of EIF2S3, and its association with patient prognosis was determined. Inducible HEL-EIF2S3 and HL-60-EIF2S3 cell lines were established by retrovirus infection. Cellular proliferation and the cell cycle were analyzed using Cell Counting Kit 8 and flow cytometric analyses. Tumorigenic ability was evaluated using xenograft nude mouse model. Gene expression profiles were analyzed in HL-60-EIF2S3 cells by next-generation sequencing, and WB analysis was performed to detect the expression of related proteins.Results The expression of EIF2S3 in patients with AML was lower than that experiencing CR (P=0.02). Furthermore, EIF2S3 overexpression inhibited cellular proliferation, halted G0/1 to S phase cell cycle progression and inhibited tumorigenicity (P=0.015). 479 differentially expressed genes were identified between HL60-EIF2S3 DOX (-) and HL60-EIF2S3 DOX (+) cells via NGS and several of them involved in MAPK/ERK signaling pathway. The phosphorylation levels of ERK decreased when EIF2S3 was overexpressed(P＜0.050).Conclusion EIF2S3 overexpression may result in a decrease in cellular proliferation, cell cycle arrest and tumorigenic inhibition via the MAPK/ERK signaling pathway in AML cells.

scholarly journals Phosphorylation by Casein Kinase 2 Facilitates rRNA Gene Transcription by Promoting Dissociation of TIF-IA from Elongating RNA Polymerase I

2008 ◽  
Vol 28 (16) ◽  
pp. 4988-4998 ◽  
Author(s):  
Holger Bierhoff ◽  
Miroslav Dundr ◽  
Annemieke A. Michels ◽  
Ingrid Grummt
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Casein Kinase ◽  
Casein Kinase 2 ◽  
Rna Polymerase I ◽  
Initiation Factor ◽  
Rrna Gene ◽  
Rdna Transcription ◽  
Pol I ◽  
Polymerase I

ABSTRACT The protein kinase casein kinase 2 (CK2) phosphorylates different components of the RNA polymerase I (Pol I) transcription machinery and exerts a positive effect on rRNA gene (rDNA) transcription. Here we show that CK2 phosphorylates the transcription initiation factor TIF-IA at serines 170 and 172 (Ser170/172), and this phosphorylation triggers the release of TIF-IA from Pol I after transcription initiation. Inhibition of Ser170/172 phosphorylation or covalent tethering of TIF-IA to the RPA43 subunit of Pol I inhibits rDNA transcription, leading to perturbation of nucleolar structure and cell cycle arrest. Fluorescence recovery after photobleaching and chromatin immunoprecipitation experiments demonstrate that dissociation of TIF-IA from Pol I is a prerequisite for proper transcription elongation. In support of phosphorylation of TIF-IA switching from the initiation into the elongation phase, dephosphorylation of Ser170/172 by FCP1 facilitates the reassociation of TIF-IA with Pol I, allowing a new round of rDNA transcription. The results reveal a mechanism by which the functional interplay between CK2 and FCP1 sustains multiple rounds of Pol I transcription.

Transcription factor TFIIIB and transcription by RNA polymerase III

2006 ◽  
Vol 34 (6) ◽  
pp. 1082-1087 ◽  
Author(s):  
G.A. Kassavetis ◽  
E.P. Geiduschek
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Transcriptional Start Site ◽  
Rna Polymerase Iii ◽  
Initiation Factor ◽  
Regulation Of Transcription ◽  
Start Site ◽  
High Mobility Group Protein ◽  
Polymerase Iii ◽  
Pol Iii

pol (RNA polymerase) III is charged with the task of transcribing nuclear genes encoding diverse small structural and catalytic RNAs. We present a brief review of the current understanding of several aspects of the pol III transcription apparatus. The focus is on yeast and, more specifically, on Saccharomyces cerevisiae; preponderant attention is given to the TFs (transcription initiation factors) and especially to TFIIIB, which is the core pol III initiation factor by virtue of its role in recruiting pol III to the transcriptional start site and its essential roles in forming the transcription-ready open promoter complex. Certain relatively recent developments are also selected for brief comment: (i) the genome-wide analysis of occupancy of pol III-transcribed genes (and other loci) by the transcription apparatus and the location of pol III transcription in the cell; (ii) progress toward a mechanistic and molecular understanding of the regulation of transcription by pol III in yeast; and (iii) recent experiments identifying a high mobility group protein as a fidelity factor that assures selection of the precise transcriptional start site at certain pol III promoters.

scholarly journals The promoter for the procyclic acidic repetitive protein (PARP) genes of Trypanosoma brucei shares features with RNA polymerase I promoters.

1992 ◽  
Vol 12 (6) ◽  
pp. 2644-2652 ◽  
Author(s):  
S D Brown ◽  
J Huang ◽  
L H Van der Ploeg
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Initiation Site ◽  
Transcription Initiation Site ◽  
Protein Coding ◽  
Pol Ii ◽  
Protein Coding Genes ◽  
Pol I ◽  
Pol Iii ◽  
Repetitive Protein

All eukaryotic protein-coding genes are believed to be transcribed by RNA polymerase (Pol) II. An exception may exist in the protozoan parasite Trypanosoma brucei, in which the genes encoding the variant surface glycoprotein (VSG) and procyclic acidic repetitive protein (PARP) are transcribed by an RNA polymerase that is resistant to the Pol II inhibitor alpha-amanitin. The PARP and VSG genes were proposed to be transcribed by Pol I (C. Shea, M. G.-S. Lee, and L. H. T. Van der Ploeg, Cell 50:603-612, 1987; G. Rudenko, M. G.-S. Lee, and L. H. T. Van der Ploeg, Nucleic Acids Res. 20:303-306, 1992), a suggestion that has been substantiated by the finding that trypanosomes can transcribe protein-coding genes by Pol I (G. Rudenko, H.-M. Chung, V. P. Pham, and L. H. T. Van der Ploeg, EMBO J. 10:3387-3397, 1991). We analyzed the sequence elements of the PARP promoter by linker scanning mutagenesis and compared the PARP promoter with Pol I, Pol II, and Pol III promoters. The PARP promoter appeared to be of limited complexity and contained at least two critical regions. The first was located adjacent to the transcription initiation site (nucleotides [nt] -69 to +12) and contained three discrete domains in which linker scanning mutants affected the transcriptional efficiency: at nt -69 to -56, -37 to -11, and -11 to +12. The second region was located between nt -140 and -131, and a third region may be located between nt -228 and -205. The nucleotide sequences of these elements, and their relative positioning with respect to the transcription initiation site did not resemble those of either Pol II or Pol III promoter elements, but rather reflected the organization of Pol I promoters in (i) similarity in the positioning of essential domains in the PARP promoter and Pol I promoter, (ii) strong sequence homology between the PARP core promoter element (nt -37 to -11) and identically positioned nucleotide sequences in the trypanosome rRNA and VSG gene promoters, and (iii) moderate effects on promoter activity of mutations around the transcription initiation site.

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