1
|
Structure of the TFIIIC subcomplex τA provides insights into RNA polymerase III pre-initiation complex formation. Nat Commun 2020; 11:4905. [PMID: 32999288 PMCID: PMC7528018 DOI: 10.1038/s41467-020-18707-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 09/08/2020] [Indexed: 01/05/2023] Open
Abstract
Transcription factor (TF) IIIC is a conserved eukaryotic six-subunit protein complex with dual function. It serves as a general TF for most RNA polymerase (Pol) III genes by recruiting TFIIIB, but it is also involved in chromatin organization and regulation of Pol II genes through interaction with CTCF and condensin II. Here, we report the structure of the S. cerevisiae TFIIIC subcomplex τA, which contains the most conserved subunits of TFIIIC and is responsible for recruitment of TFIIIB and transcription start site (TSS) selection at Pol III genes. We show that τA binding to its promoter is auto-inhibited by a disordered acidic tail of subunit τ95. We further provide a negative-stain reconstruction of τA bound to the TFIIIB subunits Brf1 and TBP. This shows that a ruler element in τA achieves positioning of TFIIIB upstream of the TSS, and suggests remodeling of the complex during assembly of TFIIIB by TFIIIC.
Collapse
|
2
|
Kling E, Spaller T, Schiefner J, Bönisch D, Winckler T. Convergent evolution of integration site selection upstream of tRNA genes by yeast and amoeba retrotransposons. Nucleic Acids Res 2019; 46:7250-7260. [PMID: 29945249 PMCID: PMC6101501 DOI: 10.1093/nar/gky582] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 06/15/2018] [Indexed: 12/17/2022] Open
Abstract
Transposable elements amplify in genomes as selfish DNA elements and challenge host fitness because their intrinsic integration steps during mobilization can compromise genome integrity. In gene-dense genomes, transposable elements are notably under selection to avoid insertional mutagenesis of host protein-coding genes. We describe an example of convergent evolution in the distantly related amoebozoan Dictyostelium discoideum and the yeast Saccharomyces cerevisiae, in which the D. discoideum retrotransposon DGLT-A and the yeast Ty3 element developed different mechanisms to facilitate position-specific integration at similar sites upstream of tRNA genes. Transcription of tRNA genes by RNA polymerase III requires the transcription factor complexes TFIIIB and TFIIIC. Whereas Ty3 recognizes tRNA genes mainly through interactions of its integrase with TFIIIB subunits, the DGLT-A-encoded ribonuclease H contacts TFIIIC subunit Tfc4 at an interface that covers tetratricopeptide repeats (TPRs) 7 and 8. A major function of this interface is to connect TFIIIC subcomplexes τA and τB and to facilitate TFIIIB assembly. During the initiation of tRNA gene transcription τB is displaced from τA, which transiently exposes the TPR 7/8 surface of Tfc4 on τA. We propose that the DGLT-A intasome uses this binding site to obtain access to genomic DNA for integration during tRNA gene transcription.
Collapse
Affiliation(s)
- Eva Kling
- Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University Jena, Germany
| | - Thomas Spaller
- Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University Jena, Germany
| | - Jana Schiefner
- Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University Jena, Germany
| | - Doreen Bönisch
- Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University Jena, Germany
| | - Thomas Winckler
- Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University Jena, Germany
| |
Collapse
|
3
|
Architecture of TFIIIC and its role in RNA polymerase III pre-initiation complex assembly. Nat Commun 2015; 6:7387. [PMID: 26060179 PMCID: PMC4490372 DOI: 10.1038/ncomms8387] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/04/2015] [Indexed: 02/05/2023] Open
Abstract
In eukaryotes, RNA Polymerase III (Pol III) is specifically responsible for transcribing genes encoding tRNAs and other short non-coding RNAs. The recruitment of Pol III to tRNA-encoding genes requires the transcription factors (TF) IIIB and IIIC. TFIIIC has been described as a conserved, multi-subunit protein complex composed of two subcomplexes, called τA and τB. How these two subcomplexes are linked and how their interaction affects the formation of the Pol III pre-initiation complex (PIC) is poorly understood. Here we use chemical crosslinking mass spectrometry and determine the molecular architecture of TFIIIC. We further report the crystal structure of the essential TPR array from τA subunit τ131 and characterize its interaction with a central region of τB subunit τ138. The identified τ131–τ138 interacting region is essential in vivo and overlaps with TFIIIB-binding sites, revealing a crucial interaction platform for the regulation of tRNA transcription initiation. TFIIIC is a RNA polymerase III-specific general transcription factor complex essential for tRNA synthesis. Here the authors combine chemical crosslinking/mass spectrometry and X-ray crystallography to define the architecture of TFIIIC and suggest a model for the assembly of pre-initiation complexes at tRNA genes.
Collapse
|
4
|
Lee J, Moir RD, Willis IM. Differential Phosphorylation of RNA Polymerase III and the Initiation Factor TFIIIB in Saccharomyces cerevisiae. PLoS One 2015; 10:e0127225. [PMID: 25970584 PMCID: PMC4430316 DOI: 10.1371/journal.pone.0127225] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/13/2015] [Indexed: 11/19/2022] Open
Abstract
The production of ribosomes and tRNAs for protein synthesis has a high energetic cost and is under tight transcriptional control to ensure that the level of RNA synthesis is balanced with nutrient availability and the prevailing environmental conditions. In the RNA polymerase (pol) III system in yeast, nutrients and stress affect transcription through a bifurcated signaling pathway in which protein kinase A (PKA) and TORC1 activity directly or indirectly, through downstream kinases, alter the phosphorylation state and function of the Maf1 repressor and Rpc53, a TFIIF-like subunit of the polymerase. However, numerous lines of evidence suggest greater complexity in the regulatory network including the phosphoregulation of other pol III components. To address this issue, we systematically examined all 17 subunits of pol III along with the three subunits of the initiation factor TFIIIB for evidence of differential phosphorylation in response to inhibition of TORC1. A relatively high stoichiometry of phosphorylation was observed for several of these proteins and the Rpc82 subunit of the polymerase and the Bdp1 subunit of TFIIIB were found to be differentially phosphorylated. Bdp1 is phosphorylated on four major sites during exponential growth and the protein is variably dephosphorylated under conditions that inhibit tRNA gene transcription. PKA, the TORC1-regulated kinase Sch9 and protein kinase CK2 are all implicated in the phosphorylation of Bdp1. Alanine substitutions at the four phosphosites cause hyper-repression of transcription indicating that phosphorylation of Bdp1 opposes Maf1-mediated repression. The new findings suggest an integrated regulatory model for signaling events controlling pol III transcription.
Collapse
Affiliation(s)
- Jaehoon Lee
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Robyn D. Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (RDM); (IMW)
| | - Ian M. Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (RDM); (IMW)
| |
Collapse
|
5
|
Tenge VR, Zuehlke AD, Shrestha N, Johnson JL. The Hsp90 cochaperones Cpr6, Cpr7, and Cns1 interact with the intact ribosome. EUKARYOTIC CELL 2015; 14:55-63. [PMID: 25380751 PMCID: PMC4279014 DOI: 10.1128/ec.00170-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 11/05/2014] [Indexed: 01/02/2023]
Abstract
The abundant molecular chaperone Hsp90 is essential for the folding and stabilization of hundreds of distinct client proteins. Hsp90 is assisted by multiple cochaperones that modulate Hsp90's ATPase activity and/or promote client interaction, but the in vivo functions of many of these cochaperones are largely unknown. We found that Cpr6, Cpr7, and Cns1 interact with the intact ribosome and that Saccharomyces cerevisiae lacking CPR7 or containing mutations in CNS1 exhibited sensitivity to the translation inhibitor hygromycin. Cpr6 contains a peptidyl-prolyl isomerase (PPIase) domain and a tetratricopeptide repeat (TPR) domain flanked by charged regions. Truncation or alteration of basic residues near the carboxy terminus of Cpr6 disrupted ribosome interaction. Cns1 contains an amino-terminal TPR domain and a poorly characterized carboxy-terminal domain. The isolated carboxy-terminal domain was able to interact with the ribosome. Although loss of CPR6 does not cause noticeable growth defects, overexpression of CPR6 results in enhanced growth defects in cells expressing the temperature-sensitive cns1-G90D mutation (the G-to-D change at position 90 encoded by cns1). Cpr6 mutants that exhibit reduced ribosome interaction failed to cause growth defects, indicating that ribosome interaction is required for in vivo functions of Cpr6. Together, these results represent a novel link between the Hsp90 molecular-chaperone machine and protein synthesis.
Collapse
Affiliation(s)
- Victoria R Tenge
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| | - Abbey D Zuehlke
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| | - Neelima Shrestha
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| | - Jill L Johnson
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| |
Collapse
|
6
|
Calderwood SK. Molecular cochaperones: tumor growth and cancer treatment. SCIENTIFICA 2013; 2013:217513. [PMID: 24278769 PMCID: PMC3820307 DOI: 10.1155/2013/217513] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/01/2013] [Indexed: 05/12/2023]
Abstract
Molecular chaperones play important roles in all cellular organisms by maintaining the proteome in an optimally folded state. They appear to be at a premium in cancer cells whose evolution along the malignant pathways requires the fostering of cohorts of mutant proteins that are employed to overcome tumor suppressive regulation. To function at significant rates in cells, HSPs interact with cochaperones, proteins that assist in catalyzing individual steps in molecular chaperoning as well as in posttranslational modification and intracellular localization. We review current knowledge regarding the roles of chaperones such as heat shock protein 90 (Hsp90) and Hsp70 and their cochaperones in cancer. Cochaperones are potential targets for cancer therapy in themselves and can be used to assess the likely prognosis of individual malignancies. Hsp70 cochaperones Bag1, Bag3, and Hop play significant roles in the etiology of some cancers as do Hsp90 cochaperones Aha1, p23, Cdc37, and FKBP1. Others such as the J domain protein family, HspBP1, TTC4, and FKBPL appear to be associated with more benign tumor phenotypes. The key importance of cochaperones for many pathways of protein folding in cancer suggests high promise for the future development of novel pharmaceutical agents.
Collapse
Affiliation(s)
- Stuart K. Calderwood
- Division of Molecular and Cellular Biology, Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, Boston, MA 02215, USA
- *Stuart K. Calderwood:
| |
Collapse
|
7
|
Moir RD, Willis IM. Regulation of pol III transcription by nutrient and stress signaling pathways. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:361-75. [PMID: 23165150 DOI: 10.1016/j.bbagrm.2012.11.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 12/29/2022]
Abstract
Transcription by RNA polymerase III (pol III) is responsible for ~15% of total cellular transcription through the generation of small structured RNAs such as tRNA and 5S RNA. The coordinate synthesis of these molecules with ribosomal protein mRNAs and rRNA couples the production of ribosomes and their tRNA substrates and balances protein synthetic capacity with the growth requirements of the cell. Ribosome biogenesis in general and pol III transcription in particular is known to be regulated by nutrient availability, cell stress and cell cycle stage and is perturbed in pathological states. High throughput proteomic studies have catalogued modifications to pol III subunits, assembly, initiation and accessory factors but most of these modifications have yet to be linked to functional consequences. Here we review our current understanding of the major points of regulation in the pol III transcription apparatus, the targets of regulation and the signaling pathways known to regulate their function. This article is part of a Special Issue entitled: Transcription by Odd Pols.
Collapse
Affiliation(s)
- Robyn D Moir
- Departments of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | |
Collapse
|
8
|
Acker J, Conesa C, Lefebvre O. Yeast RNA polymerase III transcription factors and effectors. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:283-95. [PMID: 23063749 DOI: 10.1016/j.bbagrm.2012.10.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/27/2012] [Accepted: 10/03/2012] [Indexed: 12/19/2022]
Abstract
Recent data indicate that the well-defined transcription machinery of RNA polymerase III (Pol III) is probably more complex than commonly thought. In this review, we describe the yeast basal transcription factors of Pol III and their involvements in the transcription cycle. We also present a list of proteins detected on genes transcribed by Pol III (class III genes) that might participate in the transcription process. Surprisingly, several of these proteins are involved in RNA polymerase II transcription. Defining the role of these potential new effectors in Pol III transcription in vivo will be the challenge of the next few years. This article is part of a Special Issue entitled: Transcription by Odd Pols.
Collapse
Affiliation(s)
- Joël Acker
- CEA, iBiTecS, Gif Sur Yvette, F-91191, France
| | | | | |
Collapse
|
9
|
Soragni E, Kassavetis GA. Absolute gene occupancies by RNA polymerase III, TFIIIB, and TFIIIC in Saccharomyces cerevisiae. J Biol Chem 2008; 283:26568-76. [PMID: 18667429 PMCID: PMC2546553 DOI: 10.1074/jbc.m803769200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/16/2008] [Indexed: 11/06/2022] Open
Abstract
A major limitation of chromatin immunoprecipitation lies in the challenge of measuring the immunoprecipitation effectiveness of different proteins and antibodies and the resultant inability to compare the occupancies of different DNA-binding proteins. Here we present the implementation of a quantitative chromatin immunoprecipitation assay in the RNA polymerase III (pol III) system that allowed us to measure the absolute in vivo occupancy of pol III and its two transcription factors, TFIIIC and TFIIIB, on a subset of pol III genes. The crucial point of our analysis was devising a method that allows the accurate determination of the immunoprecipitation efficiency for each protein. We achieved this by spiking every immunoprecipitation reaction with the formaldehyde cross-linked in vitro counterparts of TFIIIB-, TFIIIC-, and pol III-DNA complexes, measuring the in vitro occupancies of the corresponding factors on a DNA probe and determining probe recovery by quantitative PCR. Analysis of nine pol III-transcribed genes with diverse sequence characteristics showed a very high occupancy by TFIIIB and pol III (pol III occupancy being generally approximately 70% of TFIIIB occupancy) and a TFIIIC occupancy that ranged between approximately 5 and 25%. Current data suggest that TFIIIC is released during transcription in vitro, and it has been proposed that TFIIIB suffices for pol III recruitment in vivo. Our findings point to the transient nature of the TFIIIC-DNA interaction in vivo, with no significant counter-correlation between pol III and TFIIIC occupancy and instead to a dependence of TFIIIB-DNA and TFIIIC-DNA complex maintenance in vivo on pol III function.
Collapse
Affiliation(s)
- Elisabetta Soragni
- Division of Biological Sciences and Center for Molecular Genetics,
University of California, San Diego, La Jolla, California 92093-0634
| | - George A. Kassavetis
- Division of Biological Sciences and Center for Molecular Genetics,
University of California, San Diego, La Jolla, California 92093-0634
| |
Collapse
|
10
|
Crevel G, Bennett D, Cotterill S. The human TPR protein TTC4 is a putative Hsp90 co-chaperone which interacts with CDC6 and shows alterations in transformed cells. PLoS One 2008; 3:e0001737. [PMID: 18320024 PMCID: PMC2253824 DOI: 10.1371/journal.pone.0001737] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Accepted: 01/30/2008] [Indexed: 01/28/2023] Open
Abstract
Background The human TTC4 protein is a TPR (tetratricopeptide repeat) motif-containing protein. The gene was originally identified as being localized in a genomic region linked to breast cancer and subsequent studies on melanoma cell lines revealed point mutations in the TTC4 protein that may be associated with the progression of malignant melanoma. Methodology/Principle Findings Here we show that TTC4 is a nucleoplasmic protein which interacts with HSP90 and HSP70, and also with the replication protein CDC6. It has significant structural and functional similarities with a previously characterised Drosophila protein Dpit47. We show that TTC4 protein levels are raised in malignant melanoma cell lines compared to melanocytes. We also see increased TTC4 expression in a variety of tumour lines derived from other tissues. In addition we show that TTC4 proteins bearing some of the mutations previously identified from patient samples lose their interaction with the CDC6 protein. Conclusions/Significance Based on these results and our previous work with the Drosophila Dpit47 protein we suggest that TTC4 is an HSP90 co-chaperone protein which forms a link between HSP90 chaperone activity and DNA replication. We further suggest that the loss of the interaction with CDC6 or with additional client proteins could provide one route through which TTC4 could influence malignant development of cells.
Collapse
Affiliation(s)
- Gilles Crevel
- Department of Basic Medical Sciences, St Georges Hospital Medical School, London, United Kingdom
| | - Dorothy Bennett
- Department of Basic Medical Sciences, St Georges Hospital Medical School, London, United Kingdom
| | - Sue Cotterill
- Department of Basic Medical Sciences, St Georges Hospital Medical School, London, United Kingdom
- *E-mail:
| |
Collapse
|
11
|
Kassavetis GA, Geiduschek EP. Transcription factor TFIIIB and transcription by RNA polymerase III. Biochem Soc Trans 2007; 34:1082-7. [PMID: 17073756 DOI: 10.1042/bst0341082] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
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.
Collapse
Affiliation(s)
- G A Kassavetis
- Division of Biological Sciences and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA.
| | | |
Collapse
|
12
|
Liao Y, Moir RD, Willis IM. Interactions of Brf1 peptides with the tetratricopeptide repeat-containing subunit of TFIIIC inhibit and promote preinitiation complex assembly. Mol Cell Biol 2006; 26:5946-56. [PMID: 16880507 PMCID: PMC1592789 DOI: 10.1128/mcb.00689-06] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The binding of Brf1 to the tetratricopeptide repeat (TPR)-containing transcription factor IIIC (TFIIIC) subunit (Tfc4) represents a rate-limiting step in the ordered assembly of the RNA polymerase III initiation factor TFIIIB. Tfc4 contains multiple binding sites for Brf1 within its amino terminus and adjacent TPR arrays, but the access of Brf1 to these sites is limited by autoinhibition. Moreover, the Brf1 binding sites in Tfc4 overlap with sites important for the subsequent recruitment of another TFIIIB subunit, Bdp1, implying that repositioning of Brf1 is required after its initial interaction with Tfc4. As a starting point for dissecting the steps in TFIIIC-directed assembly of TFIIIB, we conducted yeast two-hybrid screens of Brf1 peptide libraries against different TPR-containing Tfc4 fragments. Short, biochemically active peptides were identified in three distinct regions of Brf1. Two peptides defined conserved but distal regions of Brf1 that participate in stable binding of Brf1 to TFIIIC-DNA. Remarkably, a third peptide that binds specifically to TPR6-9 of Tfc4 was found to promote the formation of both TFIIIC-DNA and Brf1-TFIIIC-DNA complexes and to reduce the mobility of these complexes in native gels. The data are consistent with this peptide causing a conformational change in TFIIIC that overcomes Tfc4 autoinhibition of Brf1 binding and suggest a structural model for the Brf1-Tfc4 interaction.
Collapse
Affiliation(s)
- Yanling Liao
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
| | | | | |
Collapse
|
13
|
Guffanti E, Ferrari R, Preti M, Forloni M, Harismendy O, Lefebvre O, Dieci G. A Minimal Promoter for TFIIIC-dependent in Vitro Transcription of snoRNA and tRNA Genes by RNA Polymerase III. J Biol Chem 2006; 281:23945-57. [PMID: 16787917 DOI: 10.1074/jbc.m513814200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae SNR52 gene is unique among the snoRNA coding genes in being transcribed by RNA polymerase III. The primary transcript of SNR52 is a 250-nucleotide precursor RNA from which a long leader sequence is cleaved to generate the mature snR52 RNA. We found that the box A and box B sequence elements in the leader region are both required for the in vivo accumulation of the snoRNA. As expected box B, but not box A, was absolutely required for stable TFIIIC, yet in vitro. Surprisingly, however, the box B was found to be largely dispensable for in vitro transcription of SNR52, whereas the box A-mutated template effectively recruited TFIIIB; yet it was transcriptionally inactive. Even in the complete absence of box B and both upstream TATA-like and T-rich elements, the box A still directed efficient, TFIIIC-dependent transcription. Box B-independent transcription was also observed for two members of the tRNA(Asn)(GTT) gene family, but not for two tRNA(Pro)(AGG) gene copies. Fully recombinant TFIIIC supported box B-independent transcription of both SNR52 and tRNA(Asn) genes, but only in the presence of TFIIIB reconstituted with a crude B'' fraction. Non-TFIIIB component(s) in this fraction were also required for transcription of wild-type SNR52. Transcription of the box B-less tRNA(Asn) genes was strongly influenced by their 5'-flanking regions, and it was stimulated by TBP and Brf1 proteins synergistically. The box A can thus be viewed as a core TFIIIC-interacting element that, assisted by upstream TFIIIB-DNA contacts, is sufficient to promote class III gene transcription.
Collapse
Affiliation(s)
- Elisa Guffanti
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, 43100 Parma, Italy
| | | | | | | | | | | | | |
Collapse
|
14
|
Dieci G, Yukawa Y, Alzapiedi M, Guffanti E, Ferrari R, Sugiura M, Ottonello S. Distinct modes of TATA box utilization by the RNA polymerase III transcription machineries from budding yeast and higher plants. Gene 2006; 379:12-25. [PMID: 16839711 DOI: 10.1016/j.gene.2006.03.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 03/23/2006] [Accepted: 03/24/2006] [Indexed: 10/24/2022]
Abstract
The TATA box is a key upstream control element for basal tRNA gene transcription by RNA polymerase III in some eukaryotes, such as the fission yeast (Schizosaccharomyces pombe) and higher plants, but not in others such as the budding yeast (Saccharomyces cerevisiae). To gain information on this differential TATA box requirement, we examined side-by-side the in vitro transcription properties of TATA-containing and TATA-mutated plant and S. cerevisiae tDNAs in homologous in vitro transcription systems from both organisms and in a hybrid system in which yeast TBP was replaced by its plant homologue. The data support the general conclusion that specific features of the plant transcription machinery, rather than upstream region architecture per se, are responsible for the much stronger TATA box dependence of the plant system. In both systems, however, a strong influence of the TATA box on transcription start site selection was observed. This was particularly striking in the case of plant tDNAs, where TATA-rich upstream regions were found to favour the use of alternative initiation sites. Replacement of yeast TBP with its plant counterpart did not confer any general TATA box responsiveness to the yeast transcription machinery. Interactions involving components other than TBP are thus responsible for the strong TATA box requirement of plant tDNA transcription.
Collapse
Affiliation(s)
- Giorgio Dieci
- Department of Biochemistry and Molecular Biology, University of Parma, Parco Area delle Scienze 23A, 43100 Parma, Italy.
| | | | | | | | | | | | | |
Collapse
|
15
|
Desai N, Lee J, Upadhya R, Chu Y, Moir RD, Willis IM. Two steps in Maf1-dependent repression of transcription by RNA polymerase III. J Biol Chem 2004; 280:6455-62. [PMID: 15590667 DOI: 10.1074/jbc.m412375200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Saccharomyces cerevisiae, Maf1 is essential for mediating the repression of transcription by RNA polymerase (pol) III in response to diverse cellular conditions. These conditions activate distinct signaling pathways that converge at or above Maf1. Thus, Maf1-dependent repression is thought to involve a common set of downstream inhibitory effects on the pol III machinery. Here we provide support for this view and define two steps in Maf1-dependent transcriptional repression. We show that chlorpromazine (CPZ)-induced repression of pol III transcription is achieved by inhibiting de novo assembly of transcription factor (TF) IIIB onto DNA as well as the recruitment of pol III to preassembled TFIIIB.DNA complexes. Additionally Brf1 was identified as a target of repression in extracts of CPZ-treated cells. Maf1-Brf1 and Maf1-pol III interactions were implicated in the inhibition of TFIIIB.DNA complex assembly and polymerase recruitment by recombinant Maf1. Co-immunoprecipitation experiments confirmed these interactions in yeast extracts and demonstrated that Maf1 does not differentially sequester Brf1 or pol III under repressing conditions. The results suggest that Maf1 functions by a non-stoichiometric mechanism to repress pol III transcription.
Collapse
Affiliation(s)
- Neelam Desai
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | | | | | | | |
Collapse
|