scholarly journals The SAGA Subunit Ada2 Functions in Transcriptional Silencing

2009 ◽  
Vol 29 (22) ◽  
pp. 6033-6045 ◽  
Author(s):  
Sandra Jacobson ◽  
Lorraine Pillus
Keyword(s):  
Transcriptional Repression ◽  
Histone Acetyltransferase ◽  
Environmental Changes ◽  
Transcriptional Silencing ◽  
Histone H4 ◽  
Nutrient Signaling ◽  
Subtelomeric Regions ◽  
Inducible Gene

ABSTRACT The cellular role of the Ada2 coactivator is currently understood in the context of the SAGA histone acetyltransferase (HAT) complex, where Ada2 increases the HAT activity of Gcn5 and interacts with transcriptional activators. Here we report a new function for Ada2 in promoting transcriptional silencing at telomeres and ribosomal DNA. This silencing function is the first characterized role for Ada2 distinct from its involvement with Gcn5. Ada2 binds telomeric chromatin and the silencing protein Sir2 in vivo. Loss of ADA2 causes the spreading of Sir2 and Sir3 into subtelomeric regions and decreased histone H4 K16 acetylation. This previously uncharacterized boundary activity of Ada2 is functionally similar to, but mechanistically distinct from, that of the MYST family HAT Sas2. Mounting evidence in the literature indicates that boundary activities create chromosomal domains important for regulating gene expression in response to environmental changes. Consistent with this, we show that upon nutritional changes, Ada2 occupancy increases at a subtelomeric region proximal to a SAGA-inducible gene and causes derepression of a silenced telomeric reporter gene. Thus, Ada2, likely in the context of SAGA, is positioned at chromosomal termini to participate in both transcriptional repression and activation in response to nutrient signaling.

scholarly journals Role of an ING1 Growth Regulator in Transcriptional Activation and Targeted Histone Acetylation by the NuA4 Complex

2001 ◽  
Vol 21 (22) ◽  
pp. 7629-7640 ◽  
Author(s):  
Amine Nourani ◽  
Yannick Doyon ◽  
Rhea T. Utley ◽  
Stéphane Allard ◽  
William S. Lane ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcription Regulation ◽  
Transcriptional Activation ◽  
Histone Acetyltransferase ◽  
Yeast Cells ◽  
Growth Defect ◽  
Histone H4 ◽  
Phd Finger

ABSTRACT The yeast NuA4 complex is a histone H4 and H2A acetyltransferase involved in transcription regulation and essential for cell cycle progression. We identify here a novel subunit of the complex, Yng2p, a plant homeodomain (PHD)-finger protein homologous to human p33/ING1, which has tumor suppressor activity and is essential for p53 function. Mass spectrometry, immunoblotting, and immunoprecipitation experiments confirm the stable stoichiometric association of this protein with purified NuA4. Yeast cells harboring a deletion of theYNG2 gene show severe growth phenotype and have gene-specific transcription defects. NuA4 complex purified from the mutant strain is low in abundance and shows weak histone acetyltransferase activity. We demonstrate conservation of function by the requirement of Yng2p for p53 to function as a transcriptional activator in yeast. Accordingly, p53 interacts with NuA4 in vitro and in vivo, an interaction reminiscent of the p53-ING1 physical link in human cells. The growth defect of Δyng2 cells can be rescued by the N-terminal part of the protein, lacking the PHD-finger. While Yng2 PHD-finger is not required for p53 interaction, it is necessary for full expression of the p53-responsive gene and other NuA4 target genes. Transcriptional activation by p53 in vivo is associated with targeted NuA4-dependent histone H4 hyperacetylation, while histone H3 acetylation levels remain unchanged. These results emphasize the essential role of the NuA4 complex in the control of cell proliferation through gene-specific transcription regulation. They also suggest that regulation of mammalian cell proliferation by p53-dependent transcriptional activation functions through recruitment of an ING1-containing histone acetyltransferase complex.

scholarly journals Slx5 Promotes Transcriptional Silencing and Is Required for Robust Growth in the Absence of Sir2

2007 ◽  
Vol 28 (4) ◽  
pp. 1361-1372 ◽  
Author(s):  
Russell P. Darst ◽  
Sandra N. Garcia ◽  
Melissa R. Koch ◽  
Lorraine Pillus
Keyword(s):  
Transcriptional Silencing ◽  
Optimal Growth ◽  
Cellular Growth ◽  
Detectable Effect ◽  
Histone H4 ◽  
Binding Assays ◽  
Ubiquitin E3 Ligase ◽  
Mutant Cells

ABSTRACT The broadly conserved Sir2 NAD+-dependent deacetylase is required for chromatin silencing. Here we report the discovery of physical and functional links between Sir2 and Slx5 (Hex3), a RING domain protein and subunit of the Slx5/8 complex column, which is a ubiquitin E3 ligase that targets sumoylated proteins. Slx5 interacted with Sir2 by two-hybrid and glutathione S-transferase-binding assays and was found to promote silencing of genes at telomeric or ribosomal DNA (rDNA) loci. However, deletion of SLX5 had no detectable effect on the distribution of silent chromatin components and only slightly altered the deacetylation of histone H4 lysine 16 at the telomere. In vivo assays indicated that Sir2-dependent silencing was functionally intact in the absence of Slx5. Although no previous reports suggest that Sir2 contributes to the fitness of yeast populations, we found that Sir2 was required for maximal growth in slx5Δ mutant cells. A similar requirement was observed for mutants of the SUMO isopeptidase Ulp2/Smt4. The contribution of Sir2 to optimal growth was not due to known Sir2 roles in mating-type determination or rDNA maintenance but was connected to a role of sumoylation in transcriptional silencing. These results indicate that Sir2 and Slx5 jointly contribute to transcriptional silencing and robust cellular growth.

scholarly journals The C-terminus of CBFβ-SMMHC is required to induce embryonic hematopoietic defects and leukemogenesis

Blood ◽  
2013 ◽  
Vol 121 (4) ◽  
pp. 638-642 ◽  
Author(s):  
Yasuhiko Kamikubo ◽  
R. Katherine Hyde ◽  
Ling Zhao ◽  
Lemlem Alemu ◽  
Cecilia Rivas ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Myeloid Leukemia ◽  
Single Copy ◽  
Full Length ◽  
Myeloproliferative Disease ◽  
Chromosome 16 ◽  
C Terminus ◽  
Acute Myeloid

Abstract The C-terminus of CBFβ-SMMHC, the fusion protein produced by a chromosome 16 inversion in acute myeloid leukemia subtype M4Eo, contains domains for self-multimerization and transcriptional repression, both of which have been proposed to be important for leukemogenesis by CBFβ-SMMHC. To test the role of the fusion protein's C-terminus in vivo, we generated knock-in mice expressing a C-terminally truncated CBFβ-SMMHC (CBFβ-SMMHCΔC95). Embryos with a single copy of CBFβ-SMMHCΔC95 were viable and showed no defects in hematopoiesis, whereas embryos homozygous for the CBFβ-SMMHCΔC95 allele had hematopoietic defects and died in mid-gestation, similar to embryos with a single-copy of the full-length CBFβ-SMMHC. Importantly, unlike mice expressing full-length CBFβ-SMMHC, none of the mice expressing CBFβ-SMMHCΔC95 developed leukemia, even after treatment with a mutagen, although some of the older mice developed a nontransplantable myeloproliferative disease. Our data indicate that the CBFβ-SMMHC's C-terminus is essential to induce embryonic hematopoietic defects and leukemogenesis.

scholarly journals Possible role of histone acetylation and histone H1° replacement for the initiation of replication in regenerating rat liver

1991 ◽  
Vol 280 (3) ◽  
pp. 777-781
Author(s):  
G Weiss ◽  
H Talasz ◽  
B Puschendorf
Keyword(s):  
Dna Synthesis ◽  
Histone Acetylation ◽  
Rat Liver ◽  
Histone Acetyltransferase ◽  
Histone H1 ◽  
Acetyltransferase Activity ◽  
Initiation Of Replication ◽  
Histone Acetyltransferase Activity

The role of histone acetylation and DNA synthesis has been investigated extensively in the regenerating rat liver system in the presence and absence of the cyclophosphamide derivative mafosfamide. We demonstrate a mafosfamide-induced inhibition of maximum histone acetyltransferase activity followed by a second elevation of enzyme activity and an accompanying total suppression of DNA synthesis for 7-8 h. The maximum of histone acetyltransferase activity, in parallel with an elevated acetylation in vivo, the consecutive replacement of histone H1(0) amd initiation of replication occur sequentially in the presence and absence of mafosfamide, but with a temporary delay of 7-8 h. Our data indicate that modifications of histone acetyltransferase (EC 2.3.1.48) activity do not significantly influence the acetylation patterns of histones H3 and H4. The mafosfamide-induced change of histone acetyltransferase activity and acetylation in vivo, the shift of histone H1(0) exchange and the consecutive transition of initiation of replication suggest that these three events might be functionally related.

scholarly journals Set2 Is a Nucleosomal Histone H3-Selective Methyltransferase That Mediates Transcriptional Repression

2002 ◽  
Vol 22 (5) ◽  
pp. 1298-1306 ◽  
Author(s):  
Brian D. Strahl ◽  
Patrick A. Grant ◽  
Scott D. Briggs ◽  
Zu-Wen Sun ◽  
James R. Bone ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Gene Activation ◽  
Limited Information ◽  
Set Domain ◽  
Biochemical Purification ◽  
Heterologous Promoter ◽  
Nucleosomal Histone

ABSTRACT Recent studies of histone methylation have yielded fundamental new insights pertaining to the role of this modification in gene activation as well as in gene silencing. While a number of methylation sites are known to occur on histones, only limited information exists regarding the relevant enzymes that mediate these methylation events. We thus sought to identify native histone methyltransferase (HMT) activities from Saccharomyces cerevisiae. Here, we describe the biochemical purification and characterization of Set2, a novel HMT that is site-specific for lysine 36 (Lys36) of the H3 tail. Using an antiserum directed against Lys36 methylation in H3, we show that Set2, via its SET domain, is responsible for methylation at this site in vivo. Tethering of Set2 to a heterologous promoter reveals that Set2 represses transcription, and part of this repression is mediated through the HMT activity of the SET domain. These results suggest that Set2 and methylation at H3 Lys36 play a role in the repression of gene transcription.

Role of GADD153 (growth arrest- and DNA damage-inducible gene 153) in vascular smooth muscle cell apoptosis

2001 ◽  
Vol 100 (3) ◽  
pp. 275-281 ◽  
Author(s):  
Michiya IGASE ◽  
Takafumi OKURA ◽  
Michitsugu NAKAMURA ◽  
Yasunori TAKATA ◽  
Yutaka KITAMI ◽  
...  
Keyword(s):  
Dna Damage ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Molecular Mechanisms ◽  
Growth Arrest ◽  
Cell Contact ◽  
Inducible Gene

GADD153 (growth arrest- and DNA damage-inducible gene 153) is expressed at very low levels in growing cells, but is markedly induced in response to a variety of cellular stresses, including glucose deprivation, exposure to genotoxic agents and other growth-arresting situations. Forced expression of GADD153 induces cell cycle arrest in many types of cells. It is also reported that GADD153 is directly associated with apoptosis. Recently we have reported that platelet-derived growth factor (PDGF)-BB induces apoptosis in cultured vascular smooth muscle cells (VSMC), but only when 100% confluency is reached. These results suggested that cell–cell contact inhibition (cell growth arrest) may be a critical factor for induction of VSMC apoptosis by PDGF-BB. In the present study, we explored the role of GADD153, one of a number of growth-arrest-related gene products, in the molecular mechanisms of VSMC apoptosis in vitro and in vivo. GADD153 was markedly induced at both the mRNA and protein levels, in parallel with the induction of VSMC apoptosis, after treatment with PDGF-BB. Moreover, overexpression of GADD153 in VSMC significantly reduced cell viability and induced apoptosis. In the carotid artery balloon injury model in rats, GADD153 protein was expressed in apoptotic VSMC which were positively stained by in situ DNA labelling. These results demonstrate an important role for GADD153 in the molecular mechanisms of VSMC apoptosis.

Histone Acetyltransferase Activity of p300 Is Required for Transcriptional Repression by the Promyelocytic Leukemia Zinc Finger Protein.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 359-359
Author(s):  
Fabien Guidez ◽  
Louise Howell ◽  
Mark Isalan ◽  
Marek Cebrat ◽  
Rhoda M. Alani ◽  
...  
Keyword(s):  
Stem Cells ◽  
Dna Binding ◽  
Histone Deacetylase ◽  
Zinc Finger ◽  
Transcriptional Repression ◽  
Promyelocytic Leukemia ◽  
Promyelocytic Leukemia Zinc Finger ◽  
Hematopoietic Stem

Abstract The Promyelocytic Leukemia Zinc Finger (PLZF) gene was identified in a rare case of acute promyelocytic leukemia (APL) with translocation t(11;17)(q23;q21) and resistance to therapy with all-trans-retinoic acid. Recent studies have indicated a critical role of PLZF in maintenance of spermatogonial stem cells. Prominent expression of PLZF in hematopoietic stem cells, suggest that it may also play a similar role in this compartment. The wild type PLZF protein is a DNA sequence-specific transcription repressor containing nine Krüppel-like C2-H2 zinc fingers and an N-terminal BTB/POZ repression domain. Transcriptional repression by PLZF is mediated through recruitment of the nuclear receptor co-repressor (N-CoR/SMRT)/histone deacetylase (HDAC) complexes to its target genes, such as c-MYC and HOX genes. We now show that transcriptional repression by PLZF is surprisingly also dependent on the histone acetyl transferase (HAT) activity of the p300 protein. PLZF associates with p300 in vivo and its ability to repress transcription is specifically dependent on acetylation of PLZF on lysines in its C-terminal C2-H2 zinc-finger motifs. Acetylation of PLZF enhances its ability to bind its cognate DNA binding site in vitro as determined by EMSA and in vivo as measured by chromatin immunoprecipitation. An acetylation site mutant of PLZF fails to repress transcription despite retaining its abilities to interact with co-repressor/HDAC complexes, due to inefficient DNA binding. Inhibitors of p300 abolish transcriptional repression by PLZF and mutants of PLZF that mimic acetylation were insensitive to these inhibitory effects. Acetylation of PLZF by p300 was specific since over-expression of another HAT, p/CAF or the selective inhibition of p/CAF had no effect on PLZF activity despite the ability of the proteins to associate with each other. Taken together, our results indicate that a histone deacetylase dependent transcriptional repressor can be positively regulated through acetylation and point to an unexpected role of a co-activator protein in transcriptional repression.

scholarly journals Nicotinamide Clearance by Pnc1 Directly Regulates Sir2-Mediated Silencing and Longevity

2004 ◽  
Vol 24 (3) ◽  
pp. 1301-1312 ◽  
Author(s):  
Christopher M. Gallo ◽  
Daniel L. Smith ◽  
Jeffrey S. Smith
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nicotinic Acid ◽  
Life Span ◽  
Histone Deacetylase ◽  
Transcriptional Repression ◽  
Transcriptional Silencing ◽  
Inhibitory Effect ◽  
Salvage Pathway

ABSTRACT The Saccharomyces cerevisiae Sir2 protein is an NAD+-dependent histone deacetylase (HDAC) that functions in transcriptional silencing and longevity. The NAD+ salvage pathway protein, Npt1, regulates Sir2-mediated processes by maintaining a sufficiently high intracellular NAD+ concentration. However, another NAD+ salvage pathway component, Pnc1, modulates silencing independently of the NAD+ concentration. Nicotinamide (NAM) is a by-product of the Sir2 deacetylase reaction and is a natural Sir2 inhibitor. Pnc1 is a nicotinamidase that converts NAM to nicotinic acid. Here we show that recombinant Pnc1 stimulates Sir2 HDAC activity in vitro by preventing the accumulation of NAM produced by Sir2. In vivo, telomeric, rDNA, and HM silencing are differentially sensitive to inhibition by NAM. Furthermore, PNC1 overexpression suppresses the inhibitory effect of exogenously added NAM on silencing, life span, and Hst1-mediated transcriptional repression. Finally, we show that stress suppresses the inhibitory effect of NAM through the induction of PNC1 expression. Pnc1, therefore, positively regulates Sir2-mediated silencing and longevity by preventing the accumulation of intracellular NAM during times of stress.

scholarly journals Hyperactivation of the Silencing Proteins, Sir2p and Sir3p, Causes Chromosome Loss

Genetics ◽  
1997 ◽  
Vol 145 (3) ◽  
pp. 605-614
Author(s):  
Scott G Holmes ◽  
Alan B Rose ◽  
Kristin Steuerle ◽  
Enrique Saez ◽  
Sandra Sayegh ◽  
...  
Keyword(s):  
Toxic Effect ◽  
Chromatin Structure ◽  
Transcriptional Repression ◽  
Yeast Cells ◽  
Chromosome Stability ◽  
Chromosome Loss ◽  
Gene Products ◽  
Histone H4 ◽  
Sir Proteins

The SIR gene products maintain transcriptional repression at the silent mating type loci and telomeres in Saccharomyces cerevisiae, although no enzymatic or structural activity has been assigned to any of the Sir proteins nor has the role of any of these proteins in transcriptional silencing been clearly defined. We have investigated the functions and interactions of the Sir2, Sir3, and Sir4 proteins by overexpressing them in yeast cells. We find that Sir2p and Sir3p are toxic when overexpressed, while high Sir4p levels have no toxic effect. Epistasis experiments indicate that Sir2p-induced toxicity is diminished in strains lacking the SIR3 gene, while both Sir2p and Sir4p are required for Sir3p to manifest its full toxic effect. In addition, the effects of Sir2 or Sir3 overexpression are exacerbated by specific mutations in the N-terminus of the histone H4 gene. These results are consistent with a model in which Sir2p, Sir3p and Sir4p function as a complex and interact with histones to modify chromatin structure. We find no evidence that toxicity from high levels of the Sir proteins results from widespread repression of transcription. Instead, we find that high levels of Sir2p and/or Sir3p cause a profound decrease in chromosome stability. These results can be appreciated in the context of the effects of Sir2p in histone acetylation and of chromatin structure on chromosome stability.

scholarly journals Human Rvb1/Tip49 Is Required for the Histone Acetyltransferase Activity of Tip60/NuA4 and for the Downregulation of Phosphorylation on H2AX after DNA Damage

2008 ◽  
Vol 28 (8) ◽  
pp. 2690-2700 ◽  
Author(s):  
Sudhakar Jha ◽  
Etsuko Shibata ◽  
Anindya Dutta
Keyword(s):  
Dna Damage ◽  
Chromatin Remodeling ◽  
Histone Acetyltransferase ◽  
Molecular Function ◽  
Histone H4 ◽  
H2ax Phosphorylation ◽  
Histone H4 Acetylation ◽  
Chromatin Remodeling Complexes ◽  
Histone Acetyltransferase Activity

ABSTRACT The role of chromatin-remodeling factors in transcription is well established, but the link between chromatin-remodeling complexes and DNA repair remains unexplored. Human Rvb1 and Rvb2 are highly conserved AAA+ ATP binding proteins that are part of various chromatin-remodeling complexes, such as Ino80, SNF2-related CBP activator protein (SRCAP), and Tip60/NuA4 complexes, but their molecular function is unclear. The depletion of Rvb1 increases the amount and persistence of phosphorylation on chromatin-associated H2AX after the exposure of cells to UV irradiation or to mitomycin C, cisplatin, camptothecin, or etoposide, without increasing the amount of DNA damage. Tip60 depletion, but not Ino80 or SRCAP depletion, mimics the effect of Rvb1 depletion on H2AX phosphorylation. Rvb1 is required for the histone acetyltransferase (HAT) activity of the Tip60 complex, and histone H4 acetylation is required prior to the dephosphorylation of phospho-H2AX. Thus, Rvb1 is critical for the dephosphorylation of phospho-H2AX due to the role of Rvb1 in maintaining the HAT activity of Tip60/NuA4, implicating the Rvb1-Tip60 complex in the chromatin-remodeling response of cells after DNA damage.

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