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The intervening domain is required for DNA-binding and functional identity of plant MADS transcription factors. Nat Commun 2021; 12:4760. [PMID: 34362909 PMCID: PMC8346517 DOI: 10.1038/s41467-021-24978-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 07/14/2021] [Indexed: 02/06/2023] Open
Abstract
The MADS transcription factors (TF) are an ancient eukaryotic protein family. In plants, the family is divided into two main lineages. Here, we demonstrate that DNA binding in both lineages absolutely requires a short amino acid sequence C-terminal to the MADS domain (M domain) called the Intervening domain (I domain) that was previously defined only in type II lineage MADS. Structural elucidation of the MI domains from the floral regulator, SEPALLATA3 (SEP3), shows a conserved fold with the I domain acting to stabilise the M domain. Using the floral organ identity MADS TFs, SEP3, APETALA1 (AP1) and AGAMOUS (AG), domain swapping demonstrate that the I domain alters genome-wide DNA-binding specificity and dimerisation specificity. Introducing AG carrying the I domain of AP1 in the Arabidopsis ap1 mutant resulted in strong complementation and restoration of first and second whorl organs. Taken together, these data demonstrate that the I domain acts as an integral part of the DNA-binding domain and significantly contributes to the functional identity of the MADS TF. MADS transcription factors regulate multiple aspects of plant development. Here the authors show that the intervening I domain is conserved in both type I and type II plant MADS lineages and contributes to the functional identity of the protein by influencing both DNA binding activity and dimerisation specificity.
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Ash1 and Tup1 dependent repression of the Saccharomyces cerevisiae HO promoter requires activator-dependent nucleosome eviction. PLoS Genet 2020; 16:e1009133. [PMID: 33382702 PMCID: PMC7806131 DOI: 10.1371/journal.pgen.1009133] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 01/13/2021] [Accepted: 11/25/2020] [Indexed: 11/30/2022] Open
Abstract
Transcriptional regulation of the Saccharomyces cerevisiae HO gene is highly complex, requiring a balance of multiple activating and repressing factors to ensure that only a few transcripts are produced in mother cells within a narrow window of the cell cycle. Here, we show that the Ash1 repressor associates with two DNA sequences that are usually concealed within nucleosomes in the HO promoter and recruits the Tup1 corepressor and the Rpd3 histone deacetylase, both of which are required for full repression in daughters. Genome-wide ChIP identified greater than 200 additional sites of co-localization of these factors, primarily within large, intergenic regions from which they could regulate adjacent genes. Most Ash1 binding sites are in nucleosome depleted regions (NDRs), while a small number overlap nucleosomes, similar to HO. We demonstrate that Ash1 binding to the HO promoter does not occur in the absence of the Swi5 transcription factor, which recruits coactivators that evict nucleosomes, including the nucleosomes obscuring the Ash1 binding sites. In the absence of Swi5, artificial nucleosome depletion allowed Ash1 to bind, demonstrating that nucleosomes are inhibitory to Ash1 binding. The location of binding sites within nucleosomes may therefore be a mechanism for limiting repressive activity to periods of nucleosome eviction that are otherwise associated with activation of the promoter. Our results illustrate that activation and repression can be intricately connected, and events set in motion by an activator may also ensure the appropriate level of repression and reset the promoter for the next activation cycle. Nucleosomes inhibit both gene expression and DNA-binding by regulatory factors. Here we examine the role of nucleosomes in regulating the binding of repressive transcription factors to the complex promoter for the yeast HO gene. Ash1 is a sequence-specific DNA-binding protein, and we show that it recruits the Tup1 global repressive factor to the HO promoter. Using a method to determine where Ash1 and Tup1 are bound to DNA throughout the genome, we discovered that Tup1 is also present at most places where Ash1 binds. The majority of these sites are in “Nucleosome Depleted Regions,” or NDRs, where the absence of chromatin makes factor binding easier. We discovered that the HO promoter is an exception, in that the two places where Ash1 binds overlap nucleosomes. Activation of the HO promoter is a complex, multi-step process, and we demonstrated that chromatin factors transiently evict these nucleosomes from the HO promoter during the cell cycle, allowing Ash1 to bind and recruit Tup1. Thus, activators must evict nucleosomes from the promoter to allow the repressive machinery to bind.
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Lai X, Stigliani A, Lucas J, Hugouvieux V, Parcy F, Zubieta C. Genome-wide binding of SEPALLATA3 and AGAMOUS complexes determined by sequential DNA-affinity purification sequencing. Nucleic Acids Res 2020; 48:9637-9648. [PMID: 32890394 PMCID: PMC7515736 DOI: 10.1093/nar/gkaa729] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 08/17/2020] [Accepted: 08/24/2020] [Indexed: 01/18/2023] Open
Abstract
The MADS transcription factors (TF), SEPALLATA3 (SEP3) and AGAMOUS (AG) are required for floral organ identity and floral meristem determinacy. While dimerization is obligatory for DNA binding, SEP3 and SEP3–AG also form tetrameric complexes. How homo and hetero-dimerization and tetramerization of MADS TFs affect genome-wide DNA-binding and gene regulation is not known. Using sequential DNA affinity purification sequencing (seq-DAP-seq), we determined genome-wide binding of SEP3 homomeric and SEP3–AG heteromeric complexes, including SEP3Δtet-AG, a complex with a SEP3 splice variant, SEP3Δtet, which is largely dimeric and SEP3–AG tetramer. SEP3 and SEP3–AG share numerous bound regions, however each complex bound unique sites, demonstrating that protein identity plays a role in DNA-binding. SEP3–AG and SEP3Δtet-AG share a similar genome-wide binding pattern; however the tetrameric form could access new sites and demonstrated a global increase in DNA-binding affinity. Tetramerization exhibited significant cooperative binding with preferential distances between two sites, allowing efficient binding to regions that are poorly recognized by dimeric SEP3Δtet-AG. By intersecting seq-DAP-seq with ChIP-seq and expression data, we identified unique target genes bound either in SEP3–AG seq-DAP-seq or in SEP3/AG ChIP-seq. Seq-DAP-seq is a versatile genome-wide technique and complements in vivo methods to identify putative direct regulatory targets.
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Affiliation(s)
- Xuelei Lai
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France
| | - Arnaud Stigliani
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, DK-2200, Denmark.,Department of Biology, University of Copenhagen, Copenhagen, DK-2200 Denmark
| | - Jérémy Lucas
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France
| | - Véronique Hugouvieux
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France
| | - François Parcy
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France
| | - Chloe Zubieta
- Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes, CNRS, CEA, INRAE, IRIG-DBSCI, 38000 Grenoble, France
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Sun CH, Yu JQ, Duan X, Wang JH, Zhang QY, Gu KD, Hu DG, Zheng CS. The MADS transcription factor CmANR1 positively modulates root system development by directly regulating CmPIN2 in chrysanthemum. HORTICULTURE RESEARCH 2018; 5:52. [PMID: 30302256 PMCID: PMC6165851 DOI: 10.1038/s41438-018-0061-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 05/23/2018] [Accepted: 05/28/2018] [Indexed: 05/20/2023]
Abstract
Plant root systems are essential for many physiological processes, including water and nutrient absorption. MADS-box transcription factor (TF) genes have been characterized as the important regulators of root development in plants; however, the underlying mechanism is largely unknown, including chrysanthemum. Here, it was found that the overexpression of CmANR1, a chrysanthemum MADS-box TF gene, promoted both adventitious root (AR) and lateral root (LR) development in chrysanthemum. Whole transcriptome sequencing analysis revealed a series of differentially expressed unigenes (DEGs) in the roots of CmANR1-transgenic chrysanthemum plants compared to wild-type plants. Functional annotation of these DEGs by alignment with Gene Ontology (GO) terms and biochemical pathway Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that CmANR1 TF exhibited "DNA binding" and "catalytic" activity, as well as participated in "phytohormone signal transduction". Both chromatin immunoprecipitation-polymerase chain reaction (ChIP-PCR) and gel electrophoresis mobility shift assays (EMSA) indicated the direct binding of CmPIN2 to the recognition site CArG-box motif by CmANR1. Finally, a firefly luciferase imaging assay demonstrated the transcriptional activation of CmPIN2 by CmANR1 in vivo. Overall, our results provide novel insights into the mechanisms of MADS-box TF CmANR1 modulation of both AR and LR development, which occurs by directly regulating auxin transport gene CmPIN2 in chrysanthemum.
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Affiliation(s)
- Cui-Hui Sun
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Jian-Qiang Yu
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Xi Duan
- Shandong Agricultural and Engineering University, Ji-Nan, Shandong China
| | - Jia-Hui Wang
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Quan-Yan Zhang
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Kai-Di Gu
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Da-Gang Hu
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
| | - Cheng-Shu Zheng
- National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018 China
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Peng YP, Zhu Y, Yin LD, Zhang JJ, Guo S, Fu Y, Miao Y, Wei JS. The Expression and Prognostic Roles of MCMs in Pancreatic Cancer. PLoS One 2016; 11:e0164150. [PMID: 27695057 PMCID: PMC5047525 DOI: 10.1371/journal.pone.0164150] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 09/20/2016] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVES Minichromosome maintenance (MCM) proteins play important roles in DNA replication by interacting with other factors which participate in the regulation of DNA synthesis. Abnormal over-expression of MCMs was observed in numerous malignancies, such as colorectal cancer. However, the expression of MCMs in pancreatic cancer (PC) was less investigated so far. This study was designed to analyze the expression and prognostic roles of MCM1-10 in PC based on the data provided by The Cancer Genome Atlas (TCGA). METHODS Pearson χ2 test was applied to evaluate the association of MCMs expression with clinicopathologic indicators, and biomarkers for tumor biological behaviors. Kaplan-Meier plots and log-rank tests were used to assess survival analysis, and univariate and multivariate Cox proportional hazard regression models were used to recognize independent prognostic factors. RESULTS MCM1-10 were generally expressed in PC samples. The levels of some molecules were markedly correlated with that of biomarkers for S phase, proliferation, gemcitabine resistance. And part of these molecules over-expression was significantly associated with indicators of disease progression, such as depth of tumor invasion and lymph node metastasis. Furthermore, MCM2, 4, 6, 8, and 10 over-expression was remarkably associated with shorter disease free survival time, and MCM2, 4,8, and 10 over-expression was associated with shorter overall survival time. Further multivariate analysis suggested that MCM8 was an independent prognostic factor for PC. CONCLUSION MCMs abnormal over-expression was significantly associated with PC progression and prognosis. These molecules could be regarded as prognostic and therapeutic biomarkers for PC. The roles of MCMs may be vitally important and the underlying mechanisms need to be furtherinvestigated.
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Affiliation(s)
- Yun-Peng Peng
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Yi Zhu
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Ling-Di Yin
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Jing-Jing Zhang
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Song Guo
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Yue Fu
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
| | - Yi Miao
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- * E-mail: (MY); (WJ-S)
| | - Ji-Shu Wei
- Pancreas Institute of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Pancreas Center, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- Department of General Surgery, The first Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China
- * E-mail: (MY); (WJ-S)
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Xiong D, Wang Y, Tian L, Tian C. MADS-Box Transcription Factor VdMcm1 Regulates Conidiation, Microsclerotia Formation, Pathogenicity, and Secondary Metabolism of Verticillium dahliae. Front Microbiol 2016; 7:1192. [PMID: 27536281 PMCID: PMC4971026 DOI: 10.3389/fmicb.2016.01192] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 07/19/2016] [Indexed: 12/02/2022] Open
Abstract
Verticillium dahliae, a notorious phytopathogenic fungus, causes vascular wilt diseases in many plant species resulting in devastating yield losses worldwide. Due to its ability to colonize plant xylem and form microsclerotia, V. dahliae is highly persistent and difficult to control. In this study, we show that the MADS-box transcription factor VdMcm1 is a key regulator of conidiation, microsclerotia formation, virulence, and secondary metabolism of V. dahliae. In addition, our findings suggest that VdMcm1 is involved in cell wall integrity. Finally, comparative RNA-Seq analysis reveals 823 significantly downregulated genes in the VdMcm1 deletion mutant, with diverse biological functions in transcriptional regulation, plant infection, cell adhesion, secondary metabolism, transmembrane transport activity, and cell secretion. When taken together, these data suggest that VdMcm1 performs pleiotropic functions in V. dahliae.
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Affiliation(s)
- Dianguang Xiong
- The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University Beijing, China
| | - Yonglin Wang
- The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University Beijing, China
| | - Longyan Tian
- The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University Beijing, China
| | - Chengming Tian
- The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University Beijing, China
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Bastajian N, Friesen H, Andrews BJ. Bck2 acts through the MADS box protein Mcm1 to activate cell-cycle-regulated genes in budding yeast. PLoS Genet 2013; 9:e1003507. [PMID: 23675312 PMCID: PMC3649975 DOI: 10.1371/journal.pgen.1003507] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 03/27/2013] [Indexed: 11/19/2022] Open
Abstract
The Bck2 protein is a potent genetic regulator of cell-cycle-dependent gene expression in budding yeast. To date, most experiments have focused on assessing a potential role for Bck2 in activation of the G1/S-specific transcription factors SBF (Swi4, Swi6) and MBF (Mbp1, Swi6), yet the mechanism of gene activation by Bck2 has remained obscure. We performed a yeast two-hybrid screen using a truncated version of Bck2 and discovered six novel Bck2-binding partners including Mcm1, an essential protein that binds to and activates M/G1 promoters through Early Cell cycle Box (ECB) elements as well as to G2/M promoters. At M/G1 promoters Mcm1 is inhibited by association with two repressors, Yox1 or Yhp1, and gene activation ensues once repression is relieved by an unknown activating signal. Here, we show that Bck2 interacts physically with Mcm1 to activate genes during G1 phase. We used chromatin immunoprecipitation (ChIP) experiments to show that Bck2 localizes to the promoters of M/G1-specific genes, in a manner dependent on functional ECB elements, as well as to the promoters of G1/S and G2/M genes. The Bck2-Mcm1 interaction requires valine 69 on Mcm1, a residue known to be required for interaction with Yox1. Overexpression of BCK2 decreases Yox1 localization to the early G1-specific CLN3 promoter and rescues the lethality caused by overexpression of YOX1. Our data suggest that Yox1 and Bck2 may compete for access to the Mcm1-ECB scaffold to ensure appropriate activation of the initial suite of genes required for cell cycle commitment.
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Affiliation(s)
- Nazareth Bastajian
- The Donnelly Centre and the Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Helena Friesen
- The Donnelly Centre and the Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Brenda J. Andrews
- The Donnelly Centre and the Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Contribution of transcription factor binding site motif variants to condition-specific gene expression patterns in budding yeast. PLoS One 2012; 7:e32274. [PMID: 22384202 PMCID: PMC3285675 DOI: 10.1371/journal.pone.0032274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 01/24/2012] [Indexed: 11/19/2022] Open
Abstract
It is now experimentally well known that variant sequences of a cis transcription factor binding site motif can contribute to differential regulation of genes. We characterize the relationship between motif variants and gene expression by analyzing expression microarray data and binding site predictions. To accomplish this, we statistically detect motif variants with effects that differ among environments. Such environmental specificity may be due to either affinity differences between variants or, more likely, differential interactions of TFs bound to these variants with cofactors, and with differential presence of cofactors across environments. We examine conservation of functional variants across four Saccharomyces species, and find that about a third of transcription factors have target genes that are differentially expressed in a condition-specific manner that is correlated with the nucleotide at variant motif positions. We find good correspondence between our results and some cases in the experimental literature (Reb1, Sum1, Mcm1, and Rap1). These results and growing consensus in the literature indicates that motif variants may often be functionally distinct, that this may be observed in genomic data, and that variants play an important role in condition-specific gene regulation.
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Coupling phosphate homeostasis to cell cycle-specific transcription: mitotic activation of Saccharomyces cerevisiae PHO5 by Mcm1 and Forkhead proteins. Mol Cell Biol 2009; 29:4891-905. [PMID: 19596791 DOI: 10.1128/mcb.00222-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cells devote considerable resources to nutrient homeostasis, involving nutrient surveillance, acquisition, and storage at physiologically relevant concentrations. Many Saccharomyces cerevisiae transcripts coding for proteins with nutrient uptake functions exhibit peak periodic accumulation during M phase, indicating that an important aspect of nutrient homeostasis involves transcriptional regulation. Inorganic phosphate is a central macronutrient that we have previously shown oscillates inversely with mitotic activation of PHO5. The mechanism of this periodic cell cycle expression remains unknown. To date, only two sequence-specific activators, Pho4 and Pho2, were known to induce PHO5 transcription. We provide here evidence that Mcm1, a MADS-box protein, is essential for PHO5 mitotic activation. In addition, we found that cells simultaneously lacking the forkhead proteins, Fkh1 and Fkh2, exhibited a 2.5-fold decrease in PHO5 expression. The Mcm1-Fkh2 complex, first shown to transactivate genes within the CLB2 cluster that drive G(2)/M progression, also associated directly at the PHO5 promoter in a cell cycle-dependent manner in chromatin immunoprecipitation assays. Sds3, a component specific to the Rpd3L histone deacetylase complex, was also recruited to PHO5 in G(1). These findings provide (i) further mechanistic insight into PHO5 mitotic activation, (ii) demonstrate that Mcm1-Fkh2 can function combinatorially with other activators to yield late M/G(1) induction, and (iii) couple the mitotic cell cycle progression machinery to cellular phosphate homeostasis.
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Tuch BB, Galgoczy DJ, Hernday AD, Li H, Johnson AD. The evolution of combinatorial gene regulation in fungi. PLoS Biol 2008; 6:e38. [PMID: 18303948 PMCID: PMC2253631 DOI: 10.1371/journal.pbio.0060038] [Citation(s) in RCA: 211] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Accepted: 01/04/2008] [Indexed: 12/20/2022] Open
Abstract
It is widely suspected that gene regulatory networks are highly plastic. The rapid turnover of transcription factor binding sites has been predicted on theoretical grounds and has been experimentally demonstrated in closely related species. We combined experimental approaches with comparative genomics to focus on the role of combinatorial control in the evolution of a large transcriptional circuit in the fungal lineage. Our study centers on Mcm1, a transcriptional regulator that, in combination with five cofactors, binds roughly 4% of the genes in Saccharomyces cerevisiae and regulates processes ranging from the cell-cycle to mating. In Kluyveromyces lactis and Candida albicans, two other hemiascomycetes, we find that the Mcm1 combinatorial circuits are substantially different. This massive rewiring of the Mcm1 circuitry has involved both substantial gain and loss of targets in ancient combinatorial circuits as well as the formation of new combinatorial interactions. We have dissected the gains and losses on the global level into subsets of functionally and temporally related changes. One particularly dramatic change is the acquisition of Mcm1 binding sites in close proximity to Rap1 binding sites at 70 ribosomal protein genes in the K. lactis lineage. Another intriguing and very recent gain occurs in the C. albicans lineage, where Mcm1 is found to bind in combination with the regulator Wor1 at many genes that function in processes associated with adaptation to the human host, including the white-opaque epigenetic switch. The large turnover of Mcm1 binding sites and the evolution of new Mcm1–cofactor interactions illuminate in sharp detail the rapid evolution of combinatorial transcription networks. In explaining the diversity of organisms on Earth, it is increasingly evident that evolutionary changes in when and where genes are expressed provide a crucial source of variation. By using genome-wide transcription factor localization experiments in S. cerevisiae, K. lactis, and C. albicans, combined with comparative genomics across many more yeast species, we examined how a large combinatorial transcription circuit evolves over the course of hundreds of millions of years. Combinatorial regulation is pervasive in eukaryotic organisms and is thought to allow for increased specificity and integration of multiple signals in the control of gene expression. Our studies focused on one prolific combinatorial regulator, Mcm1, which, in combination with five cofactors, binds and regulates genes functioning in a diverse range of cellular processes in S. cerevisiae. We found evidence of massive network rewiring, including high rates of gain and loss of Mcm1 binding sites and the formation of new Mcm1–cofactor combinations and the breaking of old ones. We propose that the multiple protein–protein and protein–DNA interactions that specify transcription in combinatorial circuits allow for a richness of compensatory mutations and thereby provide ample opportunity for both adaptive and neutral evolution. Experimental approaches combined with comparative genomics show how a large combinatorial transcription circuit has rewired over evolutionary time scales.
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Affiliation(s)
- Brian B Tuch
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
- Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - David J Galgoczy
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
- Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Aaron D Hernday
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
- Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Hao Li
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail: (HL); (ADJ)
| | - Alexander D Johnson
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
- Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail: (HL); (ADJ)
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Ito Y, Kitagawa M, Ihashi N, Yabe K, Kimbara J, Yasuda J, Ito H, Inakuma T, Hiroi S, Kasumi T. DNA-binding specificity, transcriptional activation potential, and the rin mutation effect for the tomato fruit-ripening regulator RIN. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 55:212-23. [PMID: 18363783 DOI: 10.1111/j.1365-313x.2008.03491.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The RIN gene encodes a putative MADS box transcription factor that controls tomato fruit ripening, and its ripening inhibitor (rin) mutation yields non-ripening fruit. In this study, the molecular properties of RIN and the rin mutant protein were clarified. The results revealed that the RIN protein accumulates in ripening fruit specifically and is localized in the nucleus of the cell. In vitro studies revealed that RIN forms a stable homodimer that binds to MADS domain-specific DNA sites. Analysis of binding site selection experiments revealed that the consensus binding sites of RIN highly resemble those of the SEPALLATA (SEP) proteins, which are Arabidopsis MADS box proteins that control the identity of floral organs. RIN exhibited a transcription-activating function similar to that exhibited by the SEP proteins. These results indicate that RIN exhibits similar molecular functions to SEP proteins although they play distinctly different biological roles. In vivo assays revealed that RIN binds to the cis-element of LeACS2. Our results also revealed that the rin mutant protein accumulates in the mutant fruit and exhibits a DNA-binding activity similar to that exhibited by the wild-type protein, but has lost its transcription-activating function, which in turn would inhibit ripening in mutant fruit.
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Affiliation(s)
- Yasuhiro Ito
- National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
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13
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Tsai WC, Pan ZJ, Hsiao YY, Jeng MF, Wu TF, Chen WH, Chen HH. Interactions of B-class complex proteins involved in tepal development in Phalaenopsis orchid. PLANT & CELL PHYSIOLOGY 2008; 49:814-24. [PMID: 18390881 DOI: 10.1093/pcp/pcn059] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
In our previous studies, we identified four DEFICIENS (DEF)-like genes and one GLOBOSA (GLO)-like gene involved in floral organ development in Phalaenopsis equestris. Revealing the DNA binding properties and protein-protein interactions of these floral homeotic MADS-box protein complexes (PeMADS) in orchids is crucial for the elucidation of the unique orchid floral morphogenesis. In this study, the interactome of B-class PeMADS proteins was assayed by the yeast two-hybrid system (Y2H) and glutathione S-transferase (GST) pull-down assays. Furthermore, the DNA binding activities of these proteins were assessed by using electrophoretic mobility shift assay (EMSA). All four DEF-like PeMADS proteins interacted individually with the GLO-like PeMADS6 in Y2H assay, yet with different strengths of interaction. Generally, the PeMADS3/PeMADS4 lineage interacted more strongly with PeMADS6 than the PeMADS2/PeMADS5 lineage did. In addition, independent homodimer formation for both PeMADS4 (DEF-like) and PeMADS6 (GLO-like) was detected. The protein-protein interactions between pairs of PeMADS proteins were further confirmed by using a GST pull-down assay. Furthermore, both the PeMADS4 homodimer and the PeMADS6 homodimer/homomultimer per se were able to bind to the MADS-box protein-binding motif CArG. The heterodimeric complexes PeMADS2-PeMADS6, PeMADS4-PeMADS6 and PeMADS5-PeMADS6 showed CArG binding activity. Taken together, these results suggest that various complexes formed among different combinations of the five B-class PeMADS proteins may increase the complexity of their regulatory functions and thus specify the molecular basis of whorl morphogenesis and combinatorial interactions of floral organ identity genes in orchids.
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Affiliation(s)
- Wen-Chieh Tsai
- Department of Biological Sciences and Technology, National Tainan University, Tainan 700, Taiwan
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14
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L'honore A, Rana V, Arsic N, Franckhauser C, Lamb NJ, Fernandez A. Identification of a new hybrid serum response factor and myocyte enhancer factor 2-binding element in MyoD enhancer required for MyoD expression during myogenesis. Mol Biol Cell 2007; 18:1992-2001. [PMID: 17377068 PMCID: PMC1877109 DOI: 10.1091/mbc.e06-09-0867] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Revised: 02/06/2007] [Accepted: 03/14/2007] [Indexed: 01/19/2023] Open
Abstract
MyoD is a critical myogenic factor induced rapidly upon activation of quiescent satellite cells, and required for their differentiation during muscle regeneration. One of the two enhancers of MyoD, the distal regulatory region, is essential for MyoD expression in postnatal muscle. This enhancer contains a functional divergent serum response factor (SRF)-binding CArG element required for MyoD expression during myoblast growth and muscle regeneration in vivo. Electrophoretic mobility shift assay, chromatin immunoprecipitation, and microinjection analyses show this element is a hybrid SRF- and MEF2 Binding (SMB) sequence where myocyte enhancer factor 2 (MEF2) complexes can compete out binding of SRF at the onset of differentiation. As cells differentiate into postmitotic myotubes, MyoD expression no longer requires SRF but instead MEF2 binding to this dual-specificity element. As such, the MyoD enhancer SMB element is the site for a molecular relay where MyoD expression is first initiated in activated satellite cells in an SRF-dependent manner and then increased and maintained by MEF2 binding in differentiated myotubes. Therefore, SMB is a DNA element with dual and stage-specific binding activity, which modulates the effects of regulatory proteins critical in controlling the balance between proliferation and differentiation.
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Affiliation(s)
- Aurore L'honore
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
| | - Vanessa Rana
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
| | - Nikola Arsic
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
| | - Celine Franckhauser
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
| | - Ned J. Lamb
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
| | - Anne Fernandez
- Cell Biology Unit, Institut de Génétique Humaine, Centre National de la Recherche Scientifique, 34396 Montpellier Cedex 05, France
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15
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Nikitin VP, Kozyrev SA. Transcription factor serum response factor is selectively involved in the mechanisms of long-term synapse-specific plasticity. ACTA ACUST UNITED AC 2007; 37:83-8. [PMID: 17180323 DOI: 10.1007/s11055-007-0153-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Indexed: 10/23/2022]
Abstract
Our previous studies demonstrated that acquisition of nociceptive sensitization in common snails is accompanied by long-term facilitation of the responses of defensive behavior command neurons LPl1 and RPl1 to sensory stimuli, this being dependent on the processes of translation and transcription. The mechanism of induction of long-term synaptic facilitation at the sensory inputs of neurons from chemoreceptors on the head involves cAMP and the immediate early gene transcription factor C/EBP (CCAAT-enhancer-binding protein), while regulation of the other sensory input of neurons LPl1 and RPl1 - from mechanoreceptors on the head - depends on protein kinase C. The present report describes studies of the involvement of the transcription factor serum response factor (SRF) in the processes of the synapse-specific plasticity of neuron LPl1 during the acquisition of sensitization in snails. The acquisition of sensitization during intracellular administration of oligonucleotides specifically inhibiting SRF led to the selective suppression of synaptic facilitation in the responses of neuron LPl1 to tactile stimulation of the snail's head. Synaptic facilitation of responses to chemical stimulation of the head and tactile stimulation of the foot developed just as in neurons in control sensitized animals. The results were assessed in relation to a hypothesis postulating that synapse-specific plasticity on learning may occur because of selective neurochemical "projection" of synaptic connections to various genes within neurons.
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Affiliation(s)
- V P Nikitin
- P. K. Anokhin Science Research Institute of Normal Physiology, Russian Academy of Medical Sciences, Building 4, 11 Mokhovaya Street, 103009 Moscow, Russia.
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16
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Rognon B, Kozovska Z, Coste AT, Pardini G, Sanglard D. Identification of promoter elements responsible for the regulation of MDR1 from Candida albicans, a major facilitator transporter involved in azole resistance. MICROBIOLOGY-SGM 2007; 152:3701-3722. [PMID: 17159223 DOI: 10.1099/mic.0.29277-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Upregulation of the MDR1 (multidrug resistance 1) gene is involved in the development of resistance to antifungal agents in clinical isolates of the pathogen Candida albicans. To better understand the molecular mechanisms underlying the phenomenon, the cis-acting regulatory elements present in the MDR1 promoter were characterized using a beta-galactosidase reporter system. In an azole-susceptible strain, transcription of this reporter is transiently upregulated in response to either benomyl or H(2)O(2), whereas its expression is constitutively high in an azole-resistant strain (FR2). Two cis-acting regulatory elements within the MDR1 promoter were identified that are necessary and sufficient to confer the same transcriptional responses on a heterologous promoter (CDR2). One, a benomyl response element (BRE), is situated at position -296 to -260 with respect to the ATG start codon. It is required for benomyl-dependent MDR1 upregulation and is also necessary for constitutive high expression of MDR1. A second element, termed H(2)O(2) response element (HRE), is situated at position -561 to -520. The HRE is required for H(2)O(2)-dependent MDR1 upregulation, but dispensable for constitutive high expression. Two potential binding sites (TTAG/CTAA) for the bZip transcription factor Cap1p (Candida AP-1 protein) lie within the HRE. Moreover, inactivation of CAP1 abolished the transient response to H(2)O(2). Cap1p, which has been previously implicated in cellular responses to oxidative stress, may thus play a trans-acting and positive regulatory role in the H(2)O(2)-dependent transcription of MDR1. A minimal BRE (-290 to -273) that is sufficient to detect in vitro sequence-specific binding of protein complexes in crude extracts prepared from C. albicans was also defined. Interestingly, the sequence includes a perfect match to the consensus binding sequence of Mcm1p, raising the possibility that MDR1 may be a direct target of this MADS box transcriptional activator. In conclusion, while the identity of the trans-acting factors that bind to the BRE and HRE remains to be confirmed, the tools developed during this characterization of the cis-acting elements of the MDR1 promoter should now serve to elucidate the nature of the components that modulate its activity.
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Affiliation(s)
- Bénédicte Rognon
- Institute of Microbiology, University Hospital Lausanne, Rue du Bugnon 48, CH-1011 Lausanne, Switzerland
| | - Zuzana Kozovska
- Comenius University, Faculty of Natural Sciences, Department of Microbiology and Virology, 842 15 Bratislava, Slovak Republic
| | - Alix T Coste
- Institute of Microbiology, University Hospital Lausanne, Rue du Bugnon 48, CH-1011 Lausanne, Switzerland
| | - Giacomo Pardini
- Institute of Microbiology, University Hospital Lausanne, Rue du Bugnon 48, CH-1011 Lausanne, Switzerland
| | - Dominique Sanglard
- Institute of Microbiology, University Hospital Lausanne, Rue du Bugnon 48, CH-1011 Lausanne, Switzerland
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17
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Miano JM, Long X, Fujiwara K. Serum response factor: master regulator of the actin cytoskeleton and contractile apparatus. Am J Physiol Cell Physiol 2006; 292:C70-81. [PMID: 16928770 DOI: 10.1152/ajpcell.00386.2006] [Citation(s) in RCA: 359] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Serum response factor (SRF) is a highly conserved and widely expressed, single copy transcription factor that theoretically binds up to 1,216 permutations of a 10-base pair cis element known as the CArG box. SRF-binding sites were defined initially in growth-related genes. Gene inactivation or knockdown studies in species ranging from unicellular eukaryotes to mice have consistently shown loss of SRF to be incompatible with life. However, rather than being critical for proliferation and growth, these genetic studies point to a crucial role for SRF in cellular migration and normal actin cytoskeleton and contractile biology. In fact, recent genomic studies reveal nearly half of the >200 SRF target genes encoding proteins with functions related to actin dynamics, lamellipodial/filopodial formation, integrin-cytoskeletal coupling, myofibrillogenesis, and muscle contraction. SRF has therefore emerged as a dispensable transcription factor for cellular growth but an absolutely essential orchestrator of actin cytoskeleton and contractile homeostasis. This review summarizes the recent genomic and genetic analyses of CArG-SRF that support its role as an ancient, master regulator of the actin cytoskeleton and contractile machinery.
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Affiliation(s)
- Joseph M Miano
- Cardiovascular Research Institute, University of Rochester School of Medicine, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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18
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de Folter S, Angenent GC. trans meets cis in MADS science. TRENDS IN PLANT SCIENCE 2006; 11:224-31. [PMID: 16616581 DOI: 10.1016/j.tplants.2006.03.008] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 02/03/2006] [Accepted: 03/27/2006] [Indexed: 05/08/2023]
Abstract
The interaction between a transcription factor and its binding site at the DNA is an integral part of transcriptional regulatory networks, which is fundamental for an understanding of biological processes. An example is the family of MADS domain transcription factors, which represent key regulators of processes in yeast, animals and plants. However, despite our extensive knowledge of these transcription factors, limited information is available on the cis-elements to which these proteins bind or how these elements are defined. Here, we discuss the current understanding of MADS protein binding sites and compare data from various organisms. This information can help us in developing algorithms to predict binding sites for MADS domain transcription factors, which would be a significant step forward in the identification of "down-stream" target genes and the elucidation of transcriptional networks.
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Affiliation(s)
- Stefan de Folter
- Business Unit Bioscience, Plant Research International, 6700 AA Wageningen, The Netherlands
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19
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Abstract
Cell-cycle control of transcription seems to be a universal feature of proliferating cells, although relatively little is known about its biological significance and conservation between organisms. The two distantly related yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe have provided valuable complementary insight into the regulation of periodic transcription as a function of the cell cycle. More recently, genome-wide studies of proliferating cells have identified hundreds of periodically expressed genes and underlying mechanisms of transcriptional control. This review discusses the regulation of three major transcriptional waves, which roughly coincide with three main cell-cycle transitions (initiation of DNA replication, entry into mitosis, and exit from mitosis). I also compare and contrast the transcriptional regulatory networks between the two yeasts and discuss the evolutionary conservation and possible roles for cell cycle-regulated transcription.
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Affiliation(s)
- Jürg Bähler
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom.
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20
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Sugimoto H, Okamura K, Sugimoto S, Satou M, Hattori T, Vance DE, Izumi T. Sp1 Is a Co-activator with Ets-1, and Net Is an Important Repressor of the Transcription of CTP:Phosphocholine Cytidylyltransferase α. J Biol Chem 2005; 280:40857-66. [PMID: 16157598 DOI: 10.1074/jbc.m503578200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylcholine biosynthesis via the CDP-choline pathway is primarily regulated by CTP:phosphocholine cytidylyltransferase (CT) encoded by the Pcyt1a and Pcyt1b genes. Previously, we identified an Ets-1-binding site located at -49/-47 in the promoter of Pcyt1a as an important transcriptional element involved in basal CTalpha transcription (Sugimoto, H., Sugimoto, S., Tatei, K., Obinata, H., Bakovic, M., Izumi, T., and Vance, D. E. (2003) J. Biol. Chem. 278, 19716-19722). In this study, we determined whether or not there were other important elements and binding proteins for basal CTalpha transcription in the Pcyt1a promoter, and if other Ets family proteins bind to the Ets-1-binding site. The results indicate the formation of a ternary complex with Ets-1 binding at -49/-47 and Sp1 binding at -58/-54 of the Pcyt1a promoter that is important for activating CTalpha transcription. When nuclear extracts of COS-7 cells expressing various Ets family repressors were incubated with DNA probes, binding of Net to the probes was observed. Net dose-dependently depressed the promoter-luciferase activity by 98%, even when co-expressed with Ets-1. RNA interference targeting Net caused an increase of endogenous CTalpha mRNA. After synchronizing the cell cycle in NIH3T3 cells, CTalpha mRNA increased at the S-M phase corresponding to an increase of Ets-1 mRNA and a decrease of Net mRNA. These results indicated that Net is an important endogenous repressor for CTalpha transcription.
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Affiliation(s)
- Hiroyuki Sugimoto
- Department of Molecular Biochemistry, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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21
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Granek JA, Clarke ND. Explicit equilibrium modeling of transcription-factor binding and gene regulation. Genome Biol 2005; 6:R87. [PMID: 16207358 PMCID: PMC1257470 DOI: 10.1186/gb-2005-6-10-r87] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Revised: 06/17/2005] [Accepted: 08/30/2005] [Indexed: 12/02/2022] Open
Abstract
A computational model, GOMER, is presented that predicts transcription-factor binding and incorporates effects of cooperativity and competition. We have developed a computational model that predicts the probability of transcription factor binding to any site in the genome. GOMER (generalizable occupancy model of expression regulation) calculates binding probabilities on the basis of position weight matrices, and incorporates the effects of cooperativity and competition by explicit calculation of coupled binding equilibria. GOMER can be used to test hypotheses regarding gene regulation that build upon this physically principled prediction of protein-DNA binding.
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Affiliation(s)
- Joshua A Granek
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, North Wolfe Street, Baltimore, MD 21205, USA
- National Evolutionary Synthesis Center, Broad Street, Durham, NC 27705, USA
| | - Neil D Clarke
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, North Wolfe Street, Baltimore, MD 21205, USA
- Genome Institute of Singapore, Biopolis Street, Singapore 138672, Republic of Singapore
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22
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Huet A, Parlakian A, Arnaud MC, Glandières JM, Valat P, Fermandjian S, Paulin D, Alpert B, Zentz C. Mechanism of binding of serum response factor to serum response element. FEBS J 2005; 272:3105-19. [PMID: 15955069 DOI: 10.1111/j.1742-4658.2005.04724.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Serum response factor (SRF) is a MADS transcription factor that binds to the CArG box sequence of the serum response element (SRE). Through its binding to CArG sequences, SRF activates several muscle-specific genes as well as genes that respond to mitogens. The thermodynamic parameters of the interaction of core-SRF (the 124-245 fragment of serum response factor) with specific oligonucleotides from c-fos and desmin promoters, were determined by spectroscopy. The rotational correlation time of core-SRF labeled with bis-ANS showed that the protein is monomeric at low concentration (10(-7) m). The titration curves for the fluorescence anisotropy of fluorescein-labeled oligonucleotide revealed that under equilibrium conditions, the core-SRF monomers were bound sequentially to SRE at very low concentration (10(-9) m). Curve-fitting data showed also major differences between the wild-type sequence and the oligonucleotide sequences mutated within the CArG box. The fluorescence of the core-SRF tyrosines was quenched by the SRE oligonucleotide. This quenching indicated that under stoichiometric conditions, core-SRF was bound as a dimer to the wild-type oligonucleotide, and as a monomer or a tetramer to the mutant oligonucleotides. Far-UV CD spectra indicated that the flexibility of core-SRF changed profoundly upon its binding to its specific target SRE. Lastly, the rotational correlation time of fluorescein-labeled SRE revealed that formation of the specific complex was accompanied by a change in the SRE internal dynamics. These results indicated that the flexibility of the two partners is crucial for the DNA-protein interaction.
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Affiliation(s)
- Alexis Huet
- Biologie moleculaire de la differenciation, Université Paris 7, Paris, France
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23
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Hendrix JA, Wamhoff BR, McDonald OG, Sinha S, Yoshida T, Owens GK. 5' CArG degeneracy in smooth muscle alpha-actin is required for injury-induced gene suppression in vivo. J Clin Invest 2005; 115:418-27. [PMID: 15690088 PMCID: PMC546420 DOI: 10.1172/jci22648] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2004] [Accepted: 11/09/2004] [Indexed: 01/14/2023] Open
Abstract
CC(A/T)6GG-dependent (CArG-dependent) and serum response factor-dependent (SRF-dependent) mechanisms are required for gene expression in smooth muscle cells (SMCs). However, an unusual feature of many SMC-selective promoter CArG elements is that they contain a conserved single G or C substitution in their central A/T-rich region, which reduces binding affinity for ubiquitously expressed SRF. We hypothesized that this CArG degeneracy contributes to cell-specific expression of smooth muscle alpha-actin in vivo, since substitution of c-fos consensus CArGs for the degenerate CArGs resulted in relaxed specificity in cultured cells. Surprisingly, our present results show that these substitutions have no effect on smooth muscle-specific transgene expression during normal development and maturation in transgenic mice. However, these substitutions significantly attenuated injury-induced downregulation of the mutant transgene under conditions where SRF expression was increased but expression of myocardin, a smooth muscle-selective SRF coactivator, was decreased. Finally, chromatin immunoprecipitation analyses, together with cell culture studies, suggested that myocardin selectively enhanced SRF binding to degenerate versus consensus CArG elements. Our results indicate that reductions in myocardin expression and the degeneracy of CArG elements within smooth muscle promoters play a key role in phenotypic switching of smooth muscle cells in vivo, as well as in mediating responses of CArG-dependent smooth muscle genes and growth regulatory genes under conditions in which these 2 classes of genes are differentially expressed.
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Affiliation(s)
- Jennifer A Hendrix
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA
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24
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Chang VK, Donato JJ, Chan CS, Tye BK. Mcm1 promotes replication initiation by binding specific elements at replication origins. Mol Cell Biol 2004; 24:6514-24. [PMID: 15226450 PMCID: PMC434236 DOI: 10.1128/mcb.24.14.6514-6524.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Minichromosome maintenance protein 1 (Mcm1) is required for efficient replication of autonomously replicating sequence (ARS)-containing plasmids in yeast cells. Reduced DNA binding activity in the Mcm1-1 mutant protein (P97L) results in selective initiation of a subset of replication origins and causes instability of ARS-containing plasmids. This plasmid instability in the mcm1-1 mutant can be overcome for a subset of ARSs by the inclusion of flanking sequences. Previous work showed that Mcm1 binds sequences flanking the minimal functional domains of ARSs. Here, we dissected two conserved telomeric X ARSs, ARS120 (XARS6L) and ARS131a (XARS7R), that replicate with different efficiencies in the mcm1-1 mutant. We found that additional Mcm1 binding sites in the C domain of ARS120 that are missing in ARS131a are responsible for efficient replication of ARS120 in the mcm1-1 mutant. Mutating a conserved Mcm1 binding site in the C domain diminished replication efficiency in ARS120 in wild-type cells, and increasing the number of Mcm1 binding sites stimulated replication efficiency. Our results suggest that threshold occupancy of Mcm1 in the C domain of telomeric ARSs is required for efficient initiation. We propose that origin usage in Saccharomyces cerevisiae may be regulated by the occupancy of Mcm1 at replication origins.
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Affiliation(s)
- Victoria K Chang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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25
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Rustici G, Mata J, Kivinen K, Lió P, Penkett CJ, Burns G, Hayles J, Brazma A, Nurse P, Bähler J. Periodic gene expression program of the fission yeast cell cycle. Nat Genet 2004; 36:809-17. [PMID: 15195092 DOI: 10.1038/ng1377] [Citation(s) in RCA: 354] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Accepted: 05/18/2004] [Indexed: 01/28/2023]
Abstract
Cell-cycle control of transcription seems to be universal, but little is known about its global conservation and biological significance. We report on the genome-wide transcriptional program of the Schizosaccharomyces pombe cell cycle, identifying 407 periodically expressed genes of which 136 show high-amplitude changes. These genes cluster in four major waves of expression. The forkhead protein Sep1p regulates mitotic genes in the first cluster, including Ace2p, which activates transcription in the second cluster during the M-G1 transition and cytokinesis. Other genes in the second cluster, which are required for G1-S progression, are regulated by the MBF complex independently of Sep1p and Ace2p. The third cluster coincides with S phase and a fourth cluster contains genes weakly regulated during G2 phase. Despite conserved cell-cycle transcription factors, differences in regulatory circuits between fission and budding yeasts are evident, revealing evolutionary plasticity of transcriptional control. Periodic transcription of most genes is not conserved between the two yeasts, except for a core set of approximately 40 genes that seem to be universally regulated during the eukaryotic cell cycle and may have key roles in cell-cycle progression.
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Affiliation(s)
- Gabriella Rustici
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK
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26
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Boros J, Lim FL, Darieva Z, Pic-Taylor A, Harman R, Morgan BA, Sharrocks AD. Molecular determinants of the cell-cycle regulated Mcm1p-Fkh2p transcription factor complex. Nucleic Acids Res 2003; 31:2279-88. [PMID: 12711672 PMCID: PMC154233 DOI: 10.1093/nar/gkg347] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
The MADS-box transcription factor Mcm1p and forkhead (FKH) transcription factor Fkh2p act in a DNA-bound complex to regulate cell-cycle dependent expression of the CLB2 cluster in Saccharomyces cerevisiae. Binding of Fkh2p requires prior binding by Mcm1p. Here we have investigated the molecular determinants governing the formation of the Mcm1p- Fkh2p complex. Fkh2p exhibits cooperativity in complex formation with Mcm1p and we have mapped a small region of Fkh2p located immediately upstream of the FKH DNA binding domain that is required for this cooperativity. This region is lacking in the related protein Fkh1p that cannot form ternary complexes with Mcm1p. A second region is identified that inhibits Mcm1p-independent DNA binding by Fkh2p. The spacing between the Mcm1p and Fkh2p binding sites is also a critical determinant for complex formation. We also show that Fkh2p can form ternary complexes with the human counterpart of Mcm1p, serum response factor (SRF). Mutations at analogous positions in Mcm1p, which are known to affect SRF interaction with its partner protein Elk-1, abrogate complex formation with Fkh2p, demonstrating evolutionary conservation of coregulatory protein binding surfaces. Our data therefore provide molecular insights into the mechanisms of Mcm1p- Fkh2p complex formation and more generally aid our understanding of MADS-box protein function.
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Affiliation(s)
- Joanna Boros
- School of Biological Sciences, University of Manchester, 2.205 Stopford Building, Oxford Road, Manchester M13 9PT, UK
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27
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Dzikowska A, Kacprzak M, Tomecki R, Koper M, Scazzocchio C, Weglenski P. Specific induction and carbon/nitrogen repression of arginine catabolism gene of Aspergillus nidulans--functional in vivo analysis of the otaA promoter. Fungal Genet Biol 2003; 38:175-86. [PMID: 12620254 DOI: 10.1016/s1087-1845(02)00522-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The arginine catabolism gene otaA encoding ornithine transaminase (OTAse) is specifically induced by arginine and is under the control of the broad-domain carbon and nitrogen repression systems. Arginine induction is mediated by a product of arcA gene coding for Zn(2)C(6) activator. We have identified a region responsible for arginine induction in the otaA promoter (AnUAS(arg)). Deletions within this region result in non-inducibility of OTAse by arginine, whether in an arcA(+) strain or in the presence of the arcA(d)47 gain of function allele. AnUAS(arg) is very similar to the Saccharomyces cerevisiae UAS(arg), a sequence bound by the Zn(2)C(6) activator (ArgRIIp), acting in a complex with two MADS-box proteins (McmIp and ArgRIp). We demonstrate here that two CREA in vitro binding sites in the otaA promoter are functional in vivo. CREA is directly involved in carbon repression of the otaA gene and it also reduces its basal level of expression. Although AREA binds to the otaA promoter in vitro, it probably does not participate in nitrogen metabolite repression of the gene in vivo. We show here that another putative negatively acting GATA factor AREB participates directly or indirectly in otaA nitrogen repression. We also demonstrate that the high levels of OTAse activity are an important factor in the suppression of proline auxotrophic mutations. This suppression can be achieved neither by growing of the proline auxotroph under carbon/nitrogen derepressing conditions nor by introducing of a creA(d) mutation.
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Affiliation(s)
- Agnieszka Dzikowska
- Department of Genetics, Warsaw University, ul. Pawińskiego 5A, 02-106, Warsaw, Poland.
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Calzada A, Bueno A. Genes involved in the initiation of DNA replication in yeast. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 212:133-207. [PMID: 11804036 DOI: 10.1016/s0074-7696(01)12005-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Replication and segregation of the information contained in genomic DNA are strictly regulated processes that eukaryotic cells alternate to divide successfully. Experimental work on yeast has suggested that this alternation is achieved through oscillations in the activity of a serine/threonine kinase complex, CDK, which ensures the timely activation of DNA synthesis. At the same time, this CDK-mediated activation sets up the basis of the mechanism that ensures ploidy maintenance in eukaryotes. DNA synthesis is initiated at discrete sites of the genome called origins of replication on which a prereplicative complex (pre-RC) of different protein subunits is formed during the G1 phase of the cell division cycle. Only after pre-RCs are formed is the genome competent to be replicated. Several lines of evidence suggest that CDK activity prevents the assembly of pre-RCs ensuring single rounds of genome replication during each cell division cycle. This review offers a descriptive discussion of the main molecular events that a unicellular eukaryote such as the budding yeast Saccharomyces cerevisiae undergoes to initiate DNA replication.
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Affiliation(s)
- Arturo Calzada
- Instituto de Microbiología--Bioquímica/Centro de Investigación del Cancer, Departamento de Microbiología y Genética, Edificio Departamental, CSIC/Universidad de Salamanca, Spain
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29
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Koch MA, Weisshaar B, Kroymann J, Haubold B, Mitchell-Olds T. Comparative genomics and regulatory evolution: conservation and function of the Chs and Apetala3 promoters. Mol Biol Evol 2001; 18:1882-91. [PMID: 11557794 DOI: 10.1093/oxfordjournals.molbev.a003729] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
DNA sequence variations of chalcone synthase (Chs) and Apetala3 gene promoters from 22 cruciferous plant species were analyzed to identify putative conserved regulatory elements. Our comparative approach confirmed the existence of numerous conserved sequences which may act as regulatory elements in both investigated promoters. To confirm the correct identification of a well-conserved UV-light-responsive promoter region, a subset of Chs promoter fragments were tested in Arabidopsis thaliana protoplasts. All promoters displayed similar light responsivenesses, indicating the general functional relevance of the conserved regulatory element. In addition to known regulatory elements, other highly conserved regions were detected which are likely to be of functional importance. Phylogenetic trees based on DNA sequences from both promoters (gene trees) were compared with the hypothesized phylogenetic relationships (species trees) of these taxa. The data derived from both promoter sequences were congruent with the phylogenies obtained from coding regions of other nuclear genes and from chloroplast DNA sequences. This indicates that promoter sequence evolution generally is reflective of species phylogeny. Our study also demonstrates the great value of comparative genomics and phylogenetics as a basis for functional analysis of promoter action and gene regulation.
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Affiliation(s)
- M A Koch
- Department of Botany, University of Agricultural Science, Vienna, Austria.
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30
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Kunoh T, Kaneko Y, Harashima S. Positive regulation of transcription of homeoprotein-encoding YHP1 by the two-component regulator Sln1 in Saccharomyces cerevisiae. Biochem Biophys Res Commun 2000; 278:344-8. [PMID: 11097841 DOI: 10.1006/bbrc.2000.3800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The IME1 gene is essential for initiation of meiosis in Saccharomyces cerevisiae. Transcription of IME1 is induced under starvation for nitrogen and glucose and in the presence of the MATa1 and MATalpha2 gene products. We have shown in our previous work that homeoprotein Yhp1 binds to a 28-bp region between nt -702 and -675 of the IME1 promoter in vivo and in vitro. We also revealed that the 28-bp region fused with a reporter gene harbored Yhp1-dependent URS (upstream repression sequence) activity and that the transcription of YHP1 was repressed by nonfermentable carbon source. In this study, we found, using a 5'-deletion series of the YHP1 promoter fused with a reporter gene, that the URS responsible for repression of YHP1 transcription with a nonfermentable carbon source is located at a region from nt -696 to -466 of the YHP1 promoter. We also identified and delimited a UAS (upstream activation sequence), which confers activation in both fermentable and nonfermentable carbon source media, to be from nt -356 to -306 of the YHP1 promoter. The UAS of the YHP1 promoter contained an MCE (Mcm1 control element) that is a target of the general transcription factor Mcm1 and is known to be involved in positive regulation by the two-component regulator Sln1. Consistent with this fact, the YHP1 transcription level was reduced in the Deltasln1 mutant, indicating that the two-component regulator Sln1 is involved in activation of YHP1 transcription.
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Affiliation(s)
- T Kunoh
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
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31
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Pic A, Lim FL, Ross SJ, Veal EA, Johnson AL, Sultan MR, West AG, Johnston LH, Sharrocks AD, Morgan BA. The forkhead protein Fkh2 is a component of the yeast cell cycle transcription factor SFF. EMBO J 2000; 19:3750-61. [PMID: 10899128 PMCID: PMC313965 DOI: 10.1093/emboj/19.14.3750] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2000] [Revised: 05/19/2000] [Accepted: 05/22/2000] [Indexed: 11/14/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, the MADS-box protein Mcm1, which is highly related to mammalian SRF (serum response factor), forms a ternary complex with SFF (Swi five factor) to regulate the cell cycle expression of genes such as SWI5, CLB2 and ACE2. Here we show that the forkhead protein Fkh2 is a component of SFF and is essential for ternary complex formation on the SWI5 and ACE2 promoters. Fkh2 is essential for the correct cell cycle periodicity of SWI5 and CLB2 gene expression and is phosphorylated with a timing that is consistent with a role in this expression. Furthermore, investigation of the relationship between Fkh2 and a related forkhead protein Fkh1 demonstrates that these proteins act in overlapping pathways to regulate cell morphology and cell separation. This is the first example of a eukaryotic transcription factor complex containing both a MADS-box and a forkhead protein, and it has important implications for the regulation of mammalian gene expression.
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Affiliation(s)
- A Pic
- School of Biochemistry and Genetics, The Medical School, University of Newcastle, Newcastle-upon-Tyne NE2 4HH, UK
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32
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Acton TB, Mead J, Steiner AM, Vershon AK. Scanning mutagenesis of Mcm1: residues required for DNA binding, DNA bending, and transcriptional activation by a MADS-box protein. Mol Cell Biol 2000; 20:1-11. [PMID: 10594003 PMCID: PMC85026 DOI: 10.1128/mcb.20.1.1-11.2000] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MCM1 is an essential gene in the yeast Saccharomyces cerevisiae and is a member of the MADS-box family of transcriptional regulatory factors. To understand the nature of the protein-DNA interactions of this class of proteins, we have made a series of alanine substitutions in the DNA-binding domain of Mcm1 and examined the effects of these mutations in vivo and in vitro. Our results indicate which residues of Mcm1 are important for viability, transcriptional activation, and DNA binding and bending. Substitution of residues in Mcm1 which are highly conserved among the MADS-box proteins are lethal to the cell and abolish DNA binding in vitro. These positions have almost identical interactions with DNA in both the serum response factor-DNA and alpha2-Mcm1-DNA crystal structures, suggesting that these residues make up a conserved core of protein-DNA interactions responsible for docking MADS-box proteins to DNA. Substitution of residues which are not as well conserved among members of the MADS-box family play important roles in contributing to the specificity of DNA binding. These results suggest a general model of how MADS-box proteins recognize and bind DNA. We also provide evidence that the N-terminal extension of Mcm1 may have considerable conformational freedom, possibly to allow binding to different DNA sites. Finally, we have identified two mutants at positions which are critical for Mcm1-mediated DNA bending that have a slow-growth phenotype. This finding is consistent with our earlier results, indicating that DNA bending may have a role in Mcm1 function in the cell.
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Affiliation(s)
- T B Acton
- Waksman Institute of Microbiology, Department of Molecular Biology, Rutgers University, Piscataway, New Jersey 08854-8020, USA
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33
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Abstract
Minichromosome maintenance (mcm) is an effective genetic assay for mutants defective in DNA replication. Two classes of mcm mutants have been identified using this screen: those that differentially affect the activities of certain autonomously replicating sequences (ARSs) and those that uniformly affect the activities of all ARSs. The ARS-specific MCM genes are essential for the initiation of DNA replication. Among these are members of the MCM2-7 family that encode subunits of the preinitiation complex and MCM10, whose gene product interacts with members of the Mcm2-7 proteins. Among the ARS-nonspecific MCM gene products are chromosome transmission factors. Refinement of this genetic assay as a screening tool and further analysis of existing mcm mutants may reveal new replication initiation proteins.
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Affiliation(s)
- B K Tye
- Section of Biochemistry Molecular and Cell Biology, Cornell University, Ithaca, New York 14853-2703, USA
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34
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Abstract
The use of high density DNA arrays to monitor gene expression at a genome-wide scale constitutes a fundamental advance in biology. In particular, the expression pattern of all genes in Saccharomyces cerevisiae can be interrogated using microarray analysis where cDNAs are hybridized to an array of more than 6000 genes in the yeast genome. In an effort to build a comprehensive Yeast Promoter Database and to develop new computational methods for mapping upstream regulatory elements, we started recently in an on going collaboration with experimental biologists on analysis of large-scale expression data. It is well known that complex gene expression patterns result from dynamic interacting networks of genes in the genetic regulatory circuitry. Hierarchical and modular organization of regulatory DNA sequence elements are important information for our understanding of combinatorial control of gene expression. As a bioinformatics attempt in this new direction, we have done some computational exploration of various initial experimental data. We will use cell-cycle regulated gene expression as a specific example to demonstrate how one may extract promoter information computationally from such genome-wide screening. Full report of the experiments and of the complete analysis will be published elsewhere when all the experiments are to be finished later in this year (Spellman, P.T., et al. 1998. Mol. Biol. Cell 9, 3273-3297).
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Affiliation(s)
- M Q Zhang
- Cold Spring Harbor Laboratory, NY 11724, USA.
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35
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Soh JW, Lee EH, Prywes R, Weinstein IB. Novel roles of specific isoforms of protein kinase C in activation of the c-fos serum response element. Mol Cell Biol 1999; 19:1313-24. [PMID: 9891065 PMCID: PMC116060 DOI: 10.1128/mcb.19.2.1313] [Citation(s) in RCA: 217] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/1998] [Accepted: 11/03/1998] [Indexed: 02/07/2023] Open
Abstract
Protein kinase C (PKC) is a multigene family of enzymes consisting of at least 11 isoforms. It has been implicated in the induction of c-fos and other immediate response genes by various mitogens. The serum response element (SRE) in the c-fos promoter is necessary and sufficient for induction of transcription of c-fos by serum, growth factors, and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). It forms a complex with the ternary complex factor (TCF) and with a dimer of the serum response factor (SRF). TCF is the target of several signal transduction pathways and SRF is the target of the rhoA pathway. In this study we generated dominant-negative and constitutively active mutants of PKC-alpha, PKC-delta, PKC-epsilon, and PKC-zeta to determine the roles of individual isoforms of PKC in activation of the SRE. Transient-transfection assays with NIH 3T3 cells, using an SRE-driven luciferase reporter plasmid, indicated that PKC-alpha and PKC-epsilon, but not PKC-delta or PKC-zeta, mediate SRE activation. TPA-induced activation of the SRE was partially inhibited by dominant negative c-Raf, ERK1, or ERK2, and constitutively active mutants of PKC-alpha and PKC-epsilon activated the transactivation domain of Elk-1. TPA-induced activation of the SRE was also partially inhibited by a dominant-negative MEKK1. Furthermore, TPA treatment of serum-starved NIH 3T3 cells led to phosphorylation of SEK1, and constitutively active mutants of PKC-alpha and PKC-epsilon activated the transactivation domain of c-Jun, a major substrate of JNK. Constitutively active mutants of PKC-alpha and PKC-epsilon could also induce a mutant c-fos promoter which lacks the TCF binding site, and they also induce transactivation activity of the SRF. Furthermore, rhoA-mediated SRE activation was blocked by dominant negative mutants of PKC-alpha or PKC-epsilon. Taken together, these findings indicate that PKC-alpha and PKC-epsilon can enhance the activities of at least three signaling pathways that converge on the SRE: c-Raf-MEK1-ERK-TCF, MEKK1-SEK1-JNK-TCF, and rhoA-SRF. Thus, specific isoforms of PKC may play a role in integrating networks of signal transduction pathways that control gene expression.
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Affiliation(s)
- J W Soh
- Department of Biochemistry & Molecular Biophysics, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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36
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Mendenhall MD, Hodge AE. Regulation of Cdc28 cyclin-dependent protein kinase activity during the cell cycle of the yeast Saccharomyces cerevisiae. Microbiol Mol Biol Rev 1998; 62:1191-243. [PMID: 9841670 PMCID: PMC98944 DOI: 10.1128/mmbr.62.4.1191-1243.1998] [Citation(s) in RCA: 300] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cyclin-dependent protein kinase (CDK) encoded by CDC28 is the master regulator of cell division in the budding yeast Saccharomyces cerevisiae. By mechanisms that, for the most part, remain to be delineated, Cdc28 activity controls the timing of mitotic commitment, bud initiation, DNA replication, spindle formation, and chromosome separation. Environmental stimuli and progress through the cell cycle are monitored through checkpoint mechanisms that influence Cdc28 activity at key cell cycle stages. A vast body of information concerning how Cdc28 activity is timed and coordinated with various mitotic events has accrued. This article reviews that literature. Following an introduction to the properties of CDKs common to many eukaryotic species, the key influences on Cdc28 activity-cyclin-CKI binding and phosphorylation-dephosphorylation events-are examined. The processes controlling the abundance and activity of key Cdc28 regulators, especially transcriptional and proteolytic mechanisms, are then discussed in detail. Finally, the mechanisms by which environmental stimuli influence Cdc28 activity are summarized.
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Affiliation(s)
- M D Mendenhall
- L. P. Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40536-0096, USA.
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37
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West AG, Causier BE, Davies B, Sharrocks AD. DNA binding and dimerisation determinants of Antirrhinum majus MADS-box transcription factors. Nucleic Acids Res 1998; 26:5277-87. [PMID: 9826749 PMCID: PMC148020 DOI: 10.1093/nar/26.23.5277] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Members of the MADS-box family of transcription factors are found in eukaryotes ranging from yeast to humans. In plants, MADS-box proteins regulate several developmental processes including flower, fruit and root development. We have investigated the DNA-binding mechanisms used by four such proteins in Antirrhinum majus, SQUA, PLE, DEF and GLO. SQUA differs from the characterised mammalian and yeast MADS-box proteins as it can efficiently bind two different classes of DNA-binding site. SQUA induces bending of these binding sites and the sequence of the site plays a role in determining the magnitude of these bends. Similarly, PLE and DEF/GLO induce DNA bending although the direction of the resulting bends differ. Finally, we demonstrate that the MADS-box and I-domains are sufficient for homodimer formation by SQUA. However, the K-box in SQUA can also act as an oligomerisation motif and in the full-length protein, the K-box plays a different role in mediating dimerisation in the context of SQUA homodimers or heterodimers with PLE. Together these results contribute significantly to our understanding of the function of SQUA and other plant MADS-box proteins at the molecular level.
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Affiliation(s)
- A G West
- Department of Biochemistry and Genetics, The Medical School, University of Newcastle upon Tyne, UK
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38
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Abstract
Analyses of petal and stamen development are beginning to illuminate the molecular genetic processes that are required to elaborate these organ types. Floral homeotic genes are required to specify certain organ identities, and these functions also are required throughout organogenesis. These genes, either directly or indirectly, presumably control a wide array of tissue- and cell-type-specific differentiation processes. At least part of this repertoire seems to include the regulation of cell proliferation, coupling the specification of organ identity with changes in growth dynamics in different regions of the developing flower. Furthermore, cells have an enormous amount of developmental plasticity, which means that they have to be able to integrate multiple sources of information as they terminally differentiate. Some of the identified inputs include the position of the cell in the developing organ, the status of gene expression and epigenetic information, and environmental signals. How this information is disseminated between cells is largely unknown. Not only do individual cells need to respond to this information, but fields of cells must coordinate their differentiation to form a functionally complex structure. The challenge that is before us is to understand how this plasticity of response is regulated to give a reproducible and species-specific pattern of differentiated tissues.
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Affiliation(s)
- V F Irish
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA
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39
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Escalante R, Sastre L. A Serum Response Factor homolog is required for spore differentiation in Dictyostelium. Development 1998; 125:3801-8. [PMID: 9729488 DOI: 10.1242/dev.125.19.3801] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A homolog of the Serum Response Factor (SRF) has been isolated from Dictyostelium discoideum and its function studied by analyzing the consequences of its gene disruption. The MADS-box region of Dictyostelium SRF (DdSRF) is highly conserved with those of the human, Drosophila and yeast homologs. srfA is a developmentally regulated gene expressed in prespore and spore cells. This gene plays an essential role in sporulation as its disruption leads to abnormal spore morphology and loss of viability. The mutant spores were round and cellulose deposition seemed to be partially affected. Initial prestalk and prespore cell differentiation did not seem to be compromised in the mutant since the expression of several cell-type-specific markers were found to be unaffected. However, the mRNA level of the spore marker spiA was greatly reduced. Activation of the cAMP-dependent protein kinase (PKA) by 8-Br-cAMP was not able to fully bypass the morphological defects of srfA- mutant spores, although this treatment induced spiA mRNA expression. Our results suggest that DdSRF is required for full maturation of spores and participates in the regulation of the expression of the spore-coat marker spiA and probably other maturation genes necessary for proper spore cell differentiation.
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Affiliation(s)
- R Escalante
- Instituto de Investigaciones Biomédicas del Consejo Superior de Investigaciones Científicas, C/Arturo Duperier 4, Spain.
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40
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Ellington AD, Conrad R. Aptamers as potential nucleic acid pharmaceuticals. BIOTECHNOLOGY ANNUAL REVIEW 1998; 1:185-214. [PMID: 9704089 DOI: 10.1016/s1387-2656(08)70052-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In vitro selection is a technique for the isolation of nucleic acid ligands that can bind to proteins with high affinity and specificity, and has potential applications in the development of new pharmaceuticals. This review summarizes the protein targets that have successfully elicited nucleic acid binding species (also known as "aptamers") and explores examples of how they might be developed for clinical use. In particular, the use of aptamers for the alleviation of blood clotting and the treatment of AIDS are considered.
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Affiliation(s)
- A D Ellington
- Department of Chemistry, Indiana University, Bloomington 47405, USA
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41
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Tilly JJ, Allen DW, Jack T. The CArG boxes in the promoter of the Arabidopsis floral organ identity gene APETALA3 mediate diverse regulatory effects. Development 1998; 125:1647-57. [PMID: 9521903 DOI: 10.1242/dev.125.9.1647] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
APETALA3 is a MADS box gene required for normal development of the petals and stamens in the Arabidopsis flower. Studies in yeast, mammals and plants demonstrate that MADS domain transcription factors bind with high affinity to a consensus sequence called the CArG box. The APETALA3 promoter contains three close matches to the consensus CArG box sequence. To gain insights into the APETALA3 regulatory circuitry, we have analyzed the APETALA3 promoter using AP3::uidA(GUS) fusions. 496 base pairs of APETALA3 promoter sequence 5′ to the transcriptional start directs GUS activity in the same temporal and spatial expression pattern as the APETALA3 RNA and protein in wild-type flowers. A synthetic promoter consisting of three tandem repeats of a 143 base pair sequence directs reporter gene activity exclusively to petals and stamens in the flower. We have analyzed the role of the CArG boxes by site-specific mutagenesis and find that the three CArG boxes mediate discrete regulatory effects. Mutations in CArG1 result in a decrease in reporter expression suggesting that CArG1 is the binding site for a positively acting factor or factors. Mutations in CArG2 result in a decrease in reporter expression in petals, but the expression pattern in stamens is unchanged. By contrast, mutations in CArG3 result in an increase in the level of reporter gene activity during early floral stages suggesting that CArG3 is the binding site for a negatively acting factor.
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Affiliation(s)
- J J Tilly
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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42
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Hill TA, Day CD, Zondlo SC, Thackeray AG, Irish VF. Discrete spatial and temporal cis-acting elements regulate transcription of the Arabidopsis floral homeotic gene APETALA3. Development 1998; 125:1711-21. [PMID: 9521909 DOI: 10.1242/dev.125.9.1711] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The APETALA3 floral homeotic gene is required for petal and stamen development in Arabidopsis. APETALA3 transcripts are first detected in a meristematic region that will give rise to the petal and stamen primordia, and expression is maintained in this region during subsequent development of these organs. To dissect how the APETALA3 gene is expressed in this spatially and temporally restricted domain, various APETALA3 promoter fragments were fused to the uidA reporter gene encoding beta-glucuronidase and assayed for the resulting patterns of expression in transgenic Arabidopsis plants. Based on these promoter analyses, we defined cis-acting elements required for distinct phases of APETALA3 expression, as well as for petal-specific and stamen-specific expression. By crossing the petal-specific construct into different mutant backgrounds, we have shown that several floral genes, including APETALA3, PISTILLATA, UNUSUAL FLORAL ORGANS, and APETALA1, encode trans-acting factors required for second-whorl-specific APETALA3 expression. We have also shown that the products of the APETALA1, APETALA3, PISTILLATA and AGAMOUS genes bind to several conserved sequence motifs within the APETALA3 promoter. We present a model whereby spatially and temporally restricted APETALA3 transcription is controlled via interactions between proteins binding to different domains of the APETALA3 promoter.
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Affiliation(s)
- T A Hill
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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43
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Abstract
The structure of a complex containing the homeodomain repressor protein MATalpha2 and the MADS-box transcription factor MCM1 bound to DNA has been determined by X-ray crystallography at 2.25 A resolution. It reveals the protein-protein interactions responsible for cooperative binding of MATalpha2 and MCM1 to DNA. The otherwise flexible amino-terminal extension of the MATalpha2 homeodomain forms a beta-hairpin that grips the MCM1 surface through parallel beta-strand hydrogen bonds and close-packed, predominantly hydrophobic, side chains. DNA bending induced by MCM1 brings the two proteins closer together, facilitating their interaction. An unusual feature of the complex is that an eight-amino-acid sequence adopts an alpha-helical conformation in one of two copies of the MATalpha2 monomer and a beta-strand conformation in the other. This 'chameleon' sequence of MATalpha2 may be important for recognizing natural operator sites.
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Affiliation(s)
- S Tan
- ETH-Zurich, Institut für Molekularbiologie und Biophysik, Switzerland
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44
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Madsen CS, Regan CP, Owens GK. Interaction of CArG elements and a GC-rich repressor element in transcriptional regulation of the smooth muscle myosin heavy chain gene in vascular smooth muscle cells. J Biol Chem 1997; 272:29842-51. [PMID: 9368057 DOI: 10.1074/jbc.272.47.29842] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have previously shown that maximal expression of the rat smooth muscle myosin heavy chain (SM-MHC) gene in cultured rat aortic smooth muscle cells (SMCs) required the presence of a highly conserved domain (nucleotides -1321 and -1095) that contained two positive-acting serum response factor (SRF) binding elements (CArG boxes 1 and 2) and a negative-acting GC-rich element that was recognized by Sp1 (Madsen, C. S., Hershey, J. C., Hautmann, M. B., White, S. L., and Owens, G. K. (1997) J. Biol. Chem. 272, 6332-6340). In this study, to better understand the functional role of these three cis elements, we created a series of SM-MHC reporter-gene constructs in which each element was mutated either alone or in combination with each other and tested them for activity in transient transfection assays using primary cultured rat aortic SMCs. Results demonstrated that the most proximal SRF binding element (CArG-box1) was active in the absence of CArG-box2, but only upon removal of the GC-rich repressor. In contrast, regardless of sequence context, CArG-box2 was active only when CArG-box1 was present. We further demonstrated using electrophoretic mobility shift assays that Sp1 binding to the GC-rich repressor element did not prevent SRF binding to the adjacent CArG-box2. Thus, unlike other proteins reported to inhibit SRF activity, the repressor activity associated with the GC-rich element does not appear to function through direct inhibition of SRF binding. As a first step toward understanding the importance of these elements in vivo, we performed in vivo footprinting on the intact rat aorta. We demonstrated that both CArG boxes and the GC-rich element were bound by protein within the animal. Additionally, using the rat carotid injury model we showed that Sp1 protein was significantly increased in SMCs located within the myointimal lesion, suggesting that increased expression of this putative repressor factor may contribute to the decreased SM MHC expression within SMCs found in myointimal lesions.
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Affiliation(s)
- C S Madsen
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA
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45
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Riechmann JL, Meyerowitz EM. Determination of floral organ identity by Arabidopsis MADS domain homeotic proteins AP1, AP3, PI, and AG is independent of their DNA-binding specificity. Mol Biol Cell 1997; 8:1243-59. [PMID: 9243505 PMCID: PMC276150 DOI: 10.1091/mbc.8.7.1243] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The MADS domain homeotic proteins APETALA1 (AP1), APETALA3 (AP3), PISTILLATA (PI), and AGAMOUS (AG) combinatorially specify the identity of Arabidopsis floral organs. AP1/AP1, AG/AG, and AP3/PI dimers bind to similar CArG box sequences; thus, differences in DNA-binding specificity among these proteins do not seem to be the origin of their distinct organ identity properties. To assess the overall contribution that specific DNA binding could make to their biological specificity, we have generated chimeric genes in which the amino-terminal half of the MADS domain of AP1, AP3, PI, and AG was substituted by the corresponding sequences of human SRF and MEF2A proteins. In vitro DNA-binding assays reveal that the chimeric proteins acquired the respective, and distinct, DNA-binding specificity of SRF or MEF2A. However, ectopic expression of the chimeric genes reproduces the dominant gain-of-function phenotypes exhibited by plants ectopically expressing the corresponding Arabidopsis wild-type genes. In addition, both the SRF and MEF2 chimeric genes can complement the pertinent ap1-1, ap3-3, pi-1, or ag-3 mutations to a degree similar to that of AP1, AP3, PI, and AG when expressed under the control of the same promoter. These results indicate that determination of floral organ identity by the MADS domain homeotic proteins AP1, AP3, PI, and AG is independent of their DNA-binding specificity. In addition, the DNA-binding experiments show that either one of the two MADS domains of a dimer can be sufficient to confer a particular DNA-binding specificity to the complex and that sequences outside the amino-terminal basic region of the MADS domain can, in some cases, contribute to the DNA-binding specificity of the proteins.
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Affiliation(s)
- J L Riechmann
- Division of Biology, California Institute of Technology, Pasadena 91125, USA
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46
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McInerny CJ, Partridge JF, Mikesell GE, Creemer DP, Breeden LL. A novel Mcm1-dependent element in the SWI4, CLN3, CDC6, and CDC47 promoters activates M/G1-specific transcription. Genes Dev 1997; 11:1277-88. [PMID: 9171372 DOI: 10.1101/gad.11.10.1277] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have identified a novel promoter element that confers M/G1-specific transcription in Saccharomyces cerevisiae. This element, which we call an ECB (early cell cycle box), was first identified in the SWI4 promoter, but it is also present in the promoter of a G1 cyclin CLN3, as well as in the promoters of three DNA replication genes: CDC6, CDC47, and CDC46. Transcripts from all five of these genes oscillate during the cell cycle and peak at the M/G1 boundary, as do isolated ECB elements in reporter constructs. The ECB element contains an Mcm1 binding site to which Mcm1 binds in vitro, and an Mcm1-VP16 fusion, which places a constitutive activator on Mcm1-binding sites in vivo, can deregulate ECB-containing promoters. Mcm1 is a transcription factor that is also required for minichromosome maintenance. We provide evidence that the replication defect of mcm1 mutants can be suppressed by ectopic CDC6 transcription. Periodic expression of SWI4 and CLN3 may be important for cell cycle progression, as we find that these genes are both haploinsufficient and rate limiting for G1 progression. We suggest that ECB-regulated gene products play critical roles in promoting the initiation of S-phase, both by regulating CLN1 and CLN2 transcription and as components of the initiation complex on origins of replication.
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Affiliation(s)
- C J McInerny
- Fred Hutchinson Cancer Research Center, Basic Sciences Division, Seattle, Washington 98104, USA
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47
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Dodou E, Treisman R. The Saccharomyces cerevisiae MADS-box transcription factor Rlm1 is a target for the Mpk1 mitogen-activated protein kinase pathway. Mol Cell Biol 1997; 17:1848-59. [PMID: 9121433 PMCID: PMC232032 DOI: 10.1128/mcb.17.4.1848] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Mutation of Saccharomyces cerevisiae RLM1, which encodes a MADS-box transcription factor, confers resistance to the toxic effects of constitutive activity of the Mpk1 mitogen-activated kinase (MAPK) pathway. The Rlm1 DNA-binding domain, which is similar to that of the metazoan MEF2 transcription factors, is also closely related to that of a second S. cerevisiae protein, Smp1 (second MEF2-like protein), encoded by the YBR182C open reading frame (N. Demolis et al., Yeast 10:1511-1525, 1994; H. Feldmann et al., EMBO J. 13:5795-5809, 1994). We show that Rlm1 and Smp1 have MEF2-related DNA-binding specificities: Rlm1 binds with the same specificity as MEF2, CTA(T/A)4TAG, while SMP1 binds a more extended consensus sequence, ACTACTA(T/A)4TAG. The two DNA-binding domains can heterodimerize with each other and with MEF2A. Deletion of RLM1 enhances resistance to cell wall disruptants, increases saturation density, reduces flocculation, and inactivates reporter genes controlled by the Rlm1 consensus binding site. Deletion of SMP1 neither causes these phenotypes nor enhances the Rlm1 deletion phenotype. However, overexpression of the DNA-binding domain of either protein causes an osmoremedial phenotype. Synthetic and naturally occurring MEF2 consensus sequences exhibit strong RLM1- and MPK1-dependent upstream activation sequence activity. Transcriptional activation by Rlm1 requires its C-terminal sequences, and Gal4 fusion proteins containing Rlm1 C-terminal sequences also act as MPK1-dependent transcriptional activators. These results establish the Rlm1 C-terminal sequences as a target for the Mpk1 MAPK pathway.
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Affiliation(s)
- E Dodou
- Transcription Laboratory, ICRF Laboratories, London, United Kingdom
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48
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Acton TB, Zhong H, Vershon AK. DNA-binding specificity of Mcm1: operator mutations that alter DNA-bending and transcriptional activities by a MADS box protein. Mol Cell Biol 1997; 17:1881-9. [PMID: 9121436 PMCID: PMC232035 DOI: 10.1128/mcb.17.4.1881] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The yeast Mcm1 protein is a member of the MADS box family of transcriptional regulatory factors, a class of DNA-binding proteins found in such diverse organisms as yeast, plants, flies, and humans. To explore the protein-DNA interactions of Mcm1 in vivo and in vitro, we have introduced an extensive series of base pair substitutions into an Mcm1 operator site and examined their effects on Mcm1-mediated transcriptional regulation and DNA-binding affinity. Our results show that Mcm1 uses a mechanism to contact the DNA that has some significant differences from the one used by the human serum response factor (SRF), a closely related MADS box protein in which the three-dimensional structure has been determined. One major difference is that 5-bromouracil-mediated photo-cross-linking experiments indicate that Mcm1 is in close proximity to functional groups in the major groove at the center of the recognition site whereas the SRF protein did not exhibit this characteristic. A more significant difference is that mutations at a position outside of the conserved CC(A/T)6GG site significantly reduce Mcm1-dependent DNA bending, while these substitutions have no effect on DNA bending by SRF. This result shows that the DNA bending by Mcm1 is sequence dependent and that the base-specific requirements for bending differ between Mcm1 and SRF. Interestingly, although these substitutions have a large effect on DNA bending and transcriptional activation by Mcm1, they have a relatively small effect on the DNA-binding affinity of the protein. This result suggests that the degree of DNA bending is important for transcriptional activation by Mcm1.
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Affiliation(s)
- T B Acton
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08855-0759, USA
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49
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Abstract
Serum response element binding protein (SRE BP) is a novel binding factor present in nuclear extracts of avian and NIH 3T3 fibroblasts which specifically binds to the cfos SRE within a region overlapping and immediately 3' to the CArG box. Site-directed mutagenesis combined with transfection experiments in NIH 3T3 cells showed that binding of both serum response factor (SRF) and SRE BP is necessary for maximal serum induction of the SRE. In this study, we have combined size fractionation of the SRE BP DNA binding activity with C/EBPbeta antibodies to demonstrate that homodimers and heterodimers of p35C/EBPbeta (a transactivator) and p20C/EBPbeta (a repressor) contribute to the SRE BP complex in NIH 3T3 cells. Transactivation of the SRE by p35C/EBPbeta is dependent on SRF binding but not ternary complex factor (TCF) formation. Both p35C/EBPbeta and p20C/EBPbeta bind to SRF in vitro via a carboxy-terminal domain that probably does not include the leucine zipper. Moreover, SRE mutants which retain responsiveness to the TCF-independent signaling pathway bind SRE BP in vitro with affinities that are nearly identical to that of the wild-type SRE, whereas mutant SRE.M, which is not responsive to the TCF-independent pathway, has a nearly 10-fold lower affinity for SRE BP. We propose that C/EBPbeta may play a role in conjunction with SRF in the TCF-independent signaling pathway for SRE activation.
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Affiliation(s)
- L Sealy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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50
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Kuo MH, Nadeau ET, Grayhack EJ. Multiple phosphorylated forms of the Saccharomyces cerevisiae Mcm1 protein include an isoform induced in response to high salt concentrations. Mol Cell Biol 1997; 17:819-32. [PMID: 9001236 PMCID: PMC231808 DOI: 10.1128/mcb.17.2.819] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The Saccharomyces cerevisiae Mcm1 protein is an essential multifunctional transcription factor which is highly homologous to human serum response factor. Mcm1 protein acts on a large number of distinctly regulated genes: haploid cell-type-specific genes, G2-cell-cycle-regulated genes, pheromone-induced genes, arginine metabolic genes, and genes important for cell wall and cell membrane function. We show here that Mcm1 protein is phosphorylated in vivo. Several (more than eight) isoforms of Mcm1 protein, resolved by isoelectric focusing, are present in vivo; two major phosphorylation sites lie in the N-terminal 17 amino acids immediately adjacent to the conserved MADS box DNA-binding domain. The implications of multiple species of Mcm1, particularly the notion that a unique Mcm1 isoform could be required for regulation of a specific set of Mcm1's target genes, are discussed. We also show here that Mcm1 plays an important role in the response to stress caused by NaCl. G. Yu, R. J. Deschenes, and J. S. Fassler (J. Biol. Chem. 270:8739-8743, 1995) showed that Mcm1 function is affected by mutations in the SLN1 gene, a signal transduction component implicated in the response to osmotic stress. We find that mcm1 mutations can confer either reduced or enhanced survival on high-salt medium; deletion of the N terminus or mutation in the primary phosphorylation site results in impaired growth on high-salt medium. Furthermore, Mcm1 protein is a target of a signal transduction system responsive to osmotic stress: a new isoform of Mcm1 is induced by NaCl or KCl; this result establishes that Mcm1 itself is regulated.
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Affiliation(s)
- M H Kuo
- Department of Biochemistry and Biophysics, School of Medicine, University of Rochester, New York 14642, USA
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