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Zhu Y, Vvedenskaya IO, Sze SH, Nickels BE, Kaplan CD. Quantitative analysis of transcription start site selection reveals control by DNA sequence, RNA polymerase II activity and NTP levels. Nat Struct Mol Biol 2024; 31:190-202. [PMID: 38177677 PMCID: PMC10928753 DOI: 10.1038/s41594-023-01171-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 11/03/2023] [Indexed: 01/06/2024]
Abstract
Transcription start site (TSS) selection is a key step in gene expression and occurs at many promoter positions over a wide range of efficiencies. Here we develop a massively parallel reporter assay to quantitatively dissect contributions of promoter sequence, nucleoside triphosphate substrate levels and RNA polymerase II (Pol II) activity to TSS selection by 'promoter scanning' in Saccharomyces cerevisiae (Pol II MAssively Systematic Transcript End Readout, 'Pol II MASTER'). Using Pol II MASTER, we measure the efficiency of Pol II initiation at 1,000,000 individual TSS sequences in a defined promoter context. Pol II MASTER confirms proposed critical qualities of S. cerevisiae TSS -8, -1 and +1 positions, quantitatively, in a controlled promoter context. Pol II MASTER extends quantitative analysis to surrounding sequences and determines that they tune initiation over a wide range of efficiencies. These results enabled the development of a predictive model for initiation efficiency based on sequence. We show that genetic perturbation of Pol II catalytic activity alters initiation efficiency mostly independently of TSS sequence, but selectively modulates preference for the initiating nucleotide. Intriguingly, we find that Pol II initiation efficiency is directly sensitive to guanosine-5'-triphosphate levels at the first five transcript positions and to cytosine-5'-triphosphate and uridine-5'-triphosphate levels at the second position genome wide. These results suggest individual nucleoside triphosphate levels can have transcript-specific effects on initiation, representing a cryptic layer of potential regulation at the level of Pol II biochemical properties. The results establish Pol II MASTER as a method for quantitative dissection of transcription initiation in eukaryotes.
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Affiliation(s)
- Yunye Zhu
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Irina O Vvedenskaya
- Department of Genetics and Waksman Institute, Rutgers University, Piscataway, NJ, USA
| | - Sing-Hoi Sze
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA
- Department of Computer Science and Engineering, Texas A&M University, College Station, TX, USA
| | - Bryce E Nickels
- Department of Genetics and Waksman Institute, Rutgers University, Piscataway, NJ, USA
| | - Craig D Kaplan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA.
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Li Z, Bao X, Liu X, Wang W, Yang J, Zhu X, Wang S. Transcriptome Profiling Based at Different Time Points after Hatching Deepened Our Understanding on Larval Growth and Development of Amphioctopus fangsiao. Metabolites 2023; 13:927. [PMID: 37623871 PMCID: PMC10456336 DOI: 10.3390/metabo13080927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 07/22/2023] [Accepted: 08/04/2023] [Indexed: 08/26/2023] Open
Abstract
As the quality of life improves, there is an increasing demand for nutrition-rich marine organisms like fish, shellfish, and cephalopods. To address this, artificial cultivation of these organisms is being explored along with ongoing research on their growth and development. A case in point is Amphioctopus fangsiao, a highly valued cephalopod known for its tasty meat, nutrient richness, and rapid growth rate. Despite its significance, there is a dearth of studies on the A. fangsiao growth mechanism, particularly of its larvae. In this study, we collected A. fangsiao larvae at 0, 4, 12, and 24 h post-hatching and conducted transcriptome profiling. Our analysis identified 4467, 5099, and 4181 differentially expressed genes (DEGs) at respective intervals, compared to the 0 h sample. We further analyzed the expression trends of these DEGs, noting a predominant trend of continuous upregulation. Functional exploration of this trend entailed GO and KEGG functional enrichment along with protein-protein interaction network analyses. We identified GLDC, DUSP14, DPF2, GNAI1, and ZNF271 as core genes, based on their high upregulation rate, implicated in larval growth and development. Similarly, CLTC, MEF2A, PPP1CB, PPP1R12A, and TJP1, marked by high protein interaction numbers, were identified as hub genes and the gene expression levels identified via RNA-seq analysis were validated through qRT-PCR. By analyzing the functions of key and core genes, we found that the ability of A. fangsiao larvae to metabolize carbohydrates, lipids, and other energy substances during early growth may significantly improve with the growth of the larvae. At the same time, muscle related cells in A. fangsiao larvae may develop rapidly, promoting the growth and development of larvae. Our findings provide preliminary insights into the growth and developmental mechanism of A. fangsiao, setting the stage for more comprehensive understanding and broader research into cephalopod growth and development mechanisms.
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Affiliation(s)
- Zan Li
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xiaokai Bao
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xiumei Liu
- College of Life Sciences, Yantai University, Yantai 264005, China
| | - Weijun Wang
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Jianmin Yang
- School of Agriculture, Ludong University, Yantai 264025, China
| | - Xibo Zhu
- Fishery Technology Service Center of Lanshan District, Rizhao 276800, China
| | - Shuhai Wang
- Ocean and Aquatic Research Center of Hekou District, Dongying 257200, China
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Bassett J, Rimel JK, Basu S, Basnet P, Luo J, Engel KL, Nagel M, Woyciehowsky A, Ebmeier CC, Kaplan CD, Taatjes DJ, Ranish JA. Systematic mutagenesis of TFIIH subunit p52/Tfb2 identifies residues required for XPB/Ssl2 subunit function and genetic interactions with TFB6. J Biol Chem 2022; 298:102433. [PMID: 36041630 PMCID: PMC9557730 DOI: 10.1016/j.jbc.2022.102433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 08/03/2022] [Accepted: 08/04/2022] [Indexed: 11/30/2022] Open
Abstract
TFIIH is an evolutionarily conserved complex that plays central roles in both RNA polymerase II (pol II) transcription and DNA repair. As an integral component of the pol II preinitiation complex, TFIIH regulates pol II enzyme activity in numerous ways. The TFIIH subunit XPB/Ssl2 is an ATP-dependent DNA translocase that stimulates promoter opening prior to transcription initiation. Crosslinking-mass spectrometry and cryo-EM results have shown a conserved interaction network involving XPB/Ssl2 and the C-terminal Hub region of the TFIIH p52/Tfb2 subunit, but the functional significance of specific residues is unclear. Here, we systematically mutagenized the HubA region of Tfb2 and screened for growth phenotypes in a TFB6 deletion background in Saccharomyces cerevisiae. We identified six lethal and 12 conditional mutants. Slow growth phenotypes of all but three conditional mutants were relieved in the presence of TFB6, thus identifying a functional interaction between Tfb2 HubA mutants and Tfb6, a protein that dissociates Ssl2 from TFIIH. Our biochemical analysis of Tfb2 mutants with severe growth phenotypes revealed defects in Ssl2 association, with similar results in human cells. Further characterization of these tfb2 mutant cells revealed defects in GAL gene induction, and reduced occupancy of TFIIH and pol II at GAL gene promoters, suggesting that functionally competent TFIIH is required for proper pol II recruitment to preinitiation complexes in vivo. Consistent with recent structural models of TFIIH, our results identify key residues in the p52/Tfb2 HubA domain that are required for stable incorporation of XPB/Ssl2 into TFIIH and for pol II transcription.
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Affiliation(s)
- Jacob Bassett
- Department of Systems Biology, Institute for Systems Biology, Seattle, Washington, USA
| | - Jenna K. Rimel
- Department of Biochemistry, University of Colorado, Boulder, Colorado, USA
| | - Shrabani Basu
- Department of Cell Biology, University of Pittsburgh, Pennsylvania, USA
| | - Pratik Basnet
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jie Luo
- Department of Systems Biology, Institute for Systems Biology, Seattle, Washington, USA
| | | | - Michael Nagel
- Department of Biochemistry, University of Colorado, Boulder, Colorado, USA
| | | | | | - Craig D. Kaplan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Dylan J. Taatjes
- Department of Biochemistry, University of Colorado, Boulder, Colorado, USA
| | - Jeffrey A. Ranish
- Department of Systems Biology, Institute for Systems Biology, Seattle, Washington, USA,For correspondence: Jeffrey A. Ranish
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Zhao T, Vvedenskaya IO, Lai WKM, Basu S, Pugh BF, Nickels BE, Kaplan CD. Ssl2/TFIIH function in transcription start site scanning by RNA polymerase II in Saccharomyces cerevisiae. eLife 2021; 10:e71013. [PMID: 34652274 PMCID: PMC8589449 DOI: 10.7554/elife.71013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 10/14/2021] [Indexed: 12/31/2022] Open
Abstract
In Saccharomyces cerevisiae, RNA polymerase II (Pol II) selects transcription start sites (TSSs) by a unidirectional scanning process. During scanning, a preinitiation complex (PIC) assembled at an upstream core promoter initiates at select positions within a window ~40-120 bp downstream. Several lines of evidence indicate that Ssl2, the yeast homolog of XPB and an essential and conserved subunit of the general transcription factor (GTF) TFIIH, drives scanning through its DNA-dependent ATPase activity, therefore potentially controlling both scanning rate and scanning extent (processivity). To address questions of how Ssl2 functions in promoter scanning and interacts with other initiation activities, we leveraged distinct initiation-sensitive reporters to identify novel ssl2 alleles. These ssl2 alleles, many of which alter residues conserved from yeast to human, confer either upstream or downstream TSS shifts at the model promoter ADH1 and genome-wide. Specifically, tested ssl2 alleles alter TSS selection by increasing or narrowing the distribution of TSSs used at individual promoters. Genetic interactions of ssl2 alleles with other initiation factors are consistent with ssl2 allele classes functioning through increasing or decreasing scanning processivity but not necessarily scanning rate. These alleles underpin a residue interaction network that likely modulates Ssl2 activity and TFIIH function in promoter scanning. We propose that the outcome of promoter scanning is determined by two functional networks, the first being Pol II activity and factors that modulate it to determine initiation efficiency within a scanning window, and the second being Ssl2/TFIIH and factors that modulate scanning processivity to determine the width of the scanning widow.
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Affiliation(s)
- Tingting Zhao
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - Irina O Vvedenskaya
- Department of Genetics and Waksman Institute, Rutgers UniversityPiscatawayUnited States
| | - William KM Lai
- Department of Molecular Biology and Genetics, Cornell UniversityIthacaUnited States
| | - Shrabani Basu
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
| | - B Franklin Pugh
- Department of Molecular Biology and Genetics, Cornell UniversityIthacaUnited States
| | - Bryce E Nickels
- Department of Genetics and Waksman Institute, Rutgers UniversityPiscatawayUnited States
| | - Craig D Kaplan
- Department of Biological Sciences, University of PittsburghPittsburghUnited States
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Qiu C, Jin H, Vvedenskaya I, Llenas JA, Zhao T, Malik I, Visbisky AM, Schwartz SL, Cui P, Čabart P, Han KH, Lai WKM, Metz RP, Johnson CD, Sze SH, Pugh BF, Nickels BE, Kaplan CD. Universal promoter scanning by Pol II during transcription initiation in Saccharomyces cerevisiae. Genome Biol 2020; 21:132. [PMID: 32487207 PMCID: PMC7265651 DOI: 10.1186/s13059-020-02040-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 05/08/2020] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The majority of eukaryotic promoters utilize multiple transcription start sites (TSSs). How multiple TSSs are specified at individual promoters across eukaryotes is not understood for most species. In Saccharomyces cerevisiae, a pre-initiation complex (PIC) comprised of Pol II and conserved general transcription factors (GTFs) assembles and opens DNA upstream of TSSs. Evidence from model promoters indicates that the PIC scans from upstream to downstream to identify TSSs. Prior results suggest that TSS distributions at promoters where scanning occurs shift in a polar fashion upon alteration in Pol II catalytic activity or GTF function. RESULTS To determine the extent of promoter scanning across promoter classes in S. cerevisiae, we perturb Pol II catalytic activity and GTF function and analyze their effects on TSS usage genome-wide. We find that alterations to Pol II, TFIIB, or TFIIF function widely alter the initiation landscape consistent with promoter scanning operating at all yeast promoters, regardless of promoter class. Promoter architecture, however, can determine the extent of promoter sensitivity to altered Pol II activity in ways that are predicted by a scanning model. CONCLUSIONS Our observations coupled with previous data validate key predictions of the scanning model for Pol II initiation in yeast, which we term the shooting gallery. In this model, Pol II catalytic activity and the rate and processivity of Pol II scanning together with promoter sequence determine the distribution of TSSs and their usage.
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Affiliation(s)
- Chenxi Qiu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
- Present Address: Department of Medicine, Division of Translational Therapeutics, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Huiyan Jin
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
| | - Irina Vvedenskaya
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA
| | - Jordi Abante Llenas
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, 77843-3128, USA
- Present Address: Whitaker Biomedical Engineering Institute, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Tingting Zhao
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Indranil Malik
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
- Present Address: Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Alex M Visbisky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Scott L Schwartz
- Genomics and Bioinformatics Service, Texas A&M AgriLife, College Station, TX, 77845, USA
| | - Ping Cui
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
| | - Pavel Čabart
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
- Present Address: First Faculty of Medicine, Charles University, BIOCEV, 252 42, Vestec, Czech Republic
| | - Kang Hoo Han
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA, 16802, USA
| | - William K M Lai
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA, 16802, USA
- Present Address: Department of Molecular Biology and Genetics, 458 Biotechnology, Cornell University, New York, 14853, USA
| | - Richard P Metz
- Genomics and Bioinformatics Service, Texas A&M AgriLife, College Station, TX, 77845, USA
| | - Charles D Johnson
- Genomics and Bioinformatics Service, Texas A&M AgriLife, College Station, TX, 77845, USA
| | - Sing-Hoi Sze
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA
- Department of Computer Science and Engineering, Texas A&M University, College Station, TX, 77843-3127, USA
| | - B Franklin Pugh
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA, 16802, USA
- Present Address: Department of Molecular Biology and Genetics, 458 Biotechnology, Cornell University, New York, 14853, USA
| | - Bryce E Nickels
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA
| | - Craig D Kaplan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
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Malik I, Qiu C, Snavely T, Kaplan CD. Wide-ranging and unexpected consequences of altered Pol II catalytic activity in vivo. Nucleic Acids Res 2017; 45:4431-4451. [PMID: 28119420 PMCID: PMC5416818 DOI: 10.1093/nar/gkx037] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 01/13/2017] [Indexed: 01/28/2023] Open
Abstract
Here we employ a set of RNA Polymerase II (Pol II) activity mutants to determine the consequences of increased or decreased Pol II catalysis on gene expression in Saccharomyces cerevisiae. We find that alteration of Pol II catalytic rate, either fast or slow, leads to decreased Pol II occupancy and apparent reduction in elongation rate in vivo. However, we also find that determination of elongation rate in vivo by chromatin immunoprecipitation can be confounded by the kinetics and conditions of transcriptional shutoff in the assay. We identify promoter and template-specific effects on severity of gene expression defects for both fast and slow Pol II mutants. We show that mRNA half-lives for a reporter gene are increased in both fast and slow Pol II mutant strains and the magnitude of half-life changes correlate both with mutants' growth and reporter expression defects. Finally, we tested a model that altered Pol II activity sensitizes cells to nucleotide depletion. In contrast to model predictions, mutated Pol II retains normal sensitivity to altered nucleotide levels. Our experiments establish a framework for understanding the diversity of transcription defects derived from altered Pol II activity mutants, essential for their use as probes of transcription mechanisms.
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Affiliation(s)
- Indranil Malik
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Chenxi Qiu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Thomas Snavely
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Craig D Kaplan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
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Trigger loop of RNA polymerase is a positional, not acid-base, catalyst for both transcription and proofreading. Proc Natl Acad Sci U S A 2017; 114:E5103-E5112. [PMID: 28607053 DOI: 10.1073/pnas.1702383114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The active site of multisubunit RNA polymerases (RNAPs) is highly conserved from humans to bacteria. This single site catalyzes both nucleotide addition required for RNA transcript synthesis and excision of incorrect nucleotides after misincorporation as a proofreading mechanism. Phosphoryl transfer and proofreading hydrolysis are controlled in part by a dynamic RNAP component called the trigger loop (TL), which cycles between an unfolded loop and an α-helical hairpin [trigger helices (TH)] required for rapid nucleotide addition. The precise roles of the TL/TH in RNA synthesis and hydrolysis remain unclear. An invariant histidine residue has been proposed to function in the TH form as a general acid in RNA synthesis and as a general base in RNA hydrolysis. The effects of conservative, nonionizable substitutions of the TL histidine (or a neighboring TL arginine conserved in bacteria) have not yet been rigorously tested. Here, we report that glutamine substitutions of these residues, which preserve polar interactions but are incapable of acid-base chemistry, had little effect on either phosphoryl transfer or proofreading hydrolysis by Escherichia coli RNAP. The TL substitutions did, however, affect the backtracking of RNAP necessary for proofreading and potentially the reactivity of the backtracked nucleotide. We describe a unifying model for the function of the RNAP TL, which reconciles available data and our results for representative RNAPs. This model explains diverse effects of the TL basic residues on catalysis through their effects on positioning reactants for phosphoryl transfer and easing barriers to transcript backtracking, rather than as acid-base catalysts.
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Babiychuk E, Hoang KT, Vandepoele K, Van De Slijke E, Geelen D, De Jaeger G, Obokata J, Kushnir S. The mutation nrpb1-A325V in the largest subunit of RNA polymerase II suppresses compromised growth of Arabidopsis plants deficient in a function of the general transcription factor IIF. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:730-745. [PMID: 27862530 DOI: 10.1111/tpj.13417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 10/31/2016] [Indexed: 06/06/2023]
Abstract
The evolutionarily conserved 12-subunit RNA polymerase II (Pol II) is a central catalytic component that drives RNA synthesis during the transcription cycle that consists of transcription initiation, elongation, and termination. A diverse set of general transcription factors, including a multifunctional TFIIF, govern Pol II selectivity, kinetic properties, and transcription coupling with posttranscriptional processes. Here, we show that TFIIF of Arabidopsis (Arabidopsis thaliana) resembles the metazoan complex that is composed of the TFIIFα and TFIIFβ polypeptides. Arabidopsis has two TFIIFβ subunits, of which TFIIFβ1/MAN1 is essential and TFIIFβ2/MAN2 is not. In the partial loss-of-function mutant allele man1-1, the winged helix domain of Arabidopsis TFIIFβ1/MAN1 was dispensable for plant viability, whereas the cellular organization of the shoot and root apical meristems were abnormal. Forward genetic screening identified an epistatic interaction between the largest Pol II subunit nrpb1-A325V variant and the man1-1 mutation. The suppression of the man1-1 mutant developmental defects by a mutation in Pol II suggests a link between TFIIF functions in Arabidopsis transcription cycle and the maintenance of cellular organization in the shoot and root apical meristems.
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Affiliation(s)
- Elena Babiychuk
- Vale Institute of Technology Sustainable Development, 66055-090, Belém, Pará, Brazil
| | - Khai Trinh Hoang
- Department of Plant Production, Faculty of Bioscience Engineering, Ghent University, 9000, Ghent, Belgium
- Department of Agriculture and Applied Sciences, Can Tho Technical Economic College, Can Tho, Vietnam
| | - Klaas Vandepoele
- Department of Plant Systems Biology, VIB, 9052, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium
| | - Eveline Van De Slijke
- Department of Plant Systems Biology, VIB, 9052, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium
| | - Danny Geelen
- Department of Plant Production, Faculty of Bioscience Engineering, Ghent University, 9000, Ghent, Belgium
| | - Geert De Jaeger
- Department of Plant Systems Biology, VIB, 9052, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium
| | - Junichi Obokata
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, 606-8522, Japan
| | - Sergei Kushnir
- Vale Institute of Technology Sustainable Development, 66055-090, Belém, Pará, Brazil
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High-Resolution Phenotypic Landscape of the RNA Polymerase II Trigger Loop. PLoS Genet 2016; 12:e1006321. [PMID: 27898685 PMCID: PMC5127505 DOI: 10.1371/journal.pgen.1006321] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/24/2016] [Indexed: 11/30/2022] Open
Abstract
The active sites of multisubunit RNA polymerases have a “trigger loop” (TL) that multitasks in substrate selection, catalysis, and translocation. To dissect the Saccharomyces cerevisiae RNA polymerase II TL at individual-residue resolution, we quantitatively phenotyped nearly all TL single variants en masse. Three mutant classes, revealed by phenotypes linked to transcription defects or various stresses, have distinct distributions among TL residues. We find that mutations disrupting an intra-TL hydrophobic pocket, proposed to provide a mechanism for substrate-triggered TL folding through destabilization of a catalytically inactive TL state, confer phenotypes consistent with pocket disruption and increased catalysis. Furthermore, allele-specific genetic interactions among TL and TL-proximal domain residues support the contribution of the funnel and bridge helices (BH) to TL dynamics. Our structural genetics approach incorporates structural and phenotypic data for high-resolution dissection of transcription mechanisms and their evolution, and is readily applicable to other essential yeast proteins. Proper regulation of Pol II transcription, the first step of gene expression, is essential for life. Extensive evidence has revealed a widely conserved and dynamic polymerase active site component, termed the Trigger Loop (TL), in balancing transcription rate and fidelity while possibly allowing control of transcription elongation. Coupling high-throughput sequencing with our previously established genetic system, we are able to assess the in vivo phenotypes for almost all possible single substitution Pol II TL mutants in the budding yeast Saccharomyces cerevisiae. We show that mutants in the TL nucleotide interacting and linker regions widely confer dominant and severe growth defects. Clustering of TL mutants’ transcription-related and general stress phenotypes reveals three main classes of TL mutants, including previously identified fast and slow elongating mutants. Comprehensive analyses of the distribution of fast and slow elongation mutants in light of existing Pol II crystal structures reveal critical regions contributing to proper TL dynamics and function. Evidence is presented linking a previously observed hydrophobic pocket to NTP substrate-induced TL closing, the mechanism critical for correct substrates selection and transcription fidelity. Finally, we assess the functional interplay between TL and its proximal domains, and their presumptive roles in the function and evolution of the TL. Utilizing the Pol II TL as a case study, we present a structural genetics approach that reveals insights into a complex, multi-functional, and essential domain in yeast.
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10
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Relationships Between RNA Polymerase II Activity and Spt Elongation Factors to Spt- Phenotype and Growth in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2016; 6:2489-504. [PMID: 27261007 PMCID: PMC4978902 DOI: 10.1534/g3.116.030346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The interplay between adjacent transcription units can result in transcription-dependent alterations in chromatin structure or recruitment of factors that determine transcription outcomes, including the generation of intragenic or other cryptic transcripts derived from cryptic promoters. Mutations in a number of genes in Saccharomyces cerevisiae confer both cryptic intragenic transcription and the Suppressor of Ty (Spt-) phenotype for the lys2-128∂ allele of the LYS2 gene. Mutants that suppress lys2-128∂ allow transcription from a normally inactive Ty1 ∂ promoter, conferring a LYS+ phenotype. The arrangement of transcription units at lys2-128∂ is reminiscent of genes containing cryptic promoters within their open reading frames. We set out to examine the relationship between RNA Polymerase II (Pol II) activity, functions of Spt elongation factors, and cryptic transcription because of the previous observation that increased-activity Pol II alleles confer an Spt- phenotype. We identify both cooperating and antagonistic genetic interactions between Pol II alleles and alleles of elongation factors SPT4, SPT5, and SPT6. We find that cryptic transcription at FLO8 and STE11 is distinct from that at lys2-128∂, though all show sensitivity to reduction in Pol II activity, especially the expression of lys2-128∂ found in Spt- mutants. We determine that the lys2-128∂ Spt- phenotypes for spt6-1004 and increased activity rpo21/rpb1 alleles each require transcription from the LYS2 promoter. Furthermore, we identify the Ty1 transcription start site (TSS) within the ∂ element as the position of Spt- transcription in tested Spt- mutants.
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