scholarly journals Transformation by the Bmi-1 oncoprotein correlates with its subnuclear localization but not its transcriptional suppression activity.

1996 ◽  
Vol 16 (10) ◽  
pp. 5527-5535 ◽  
Author(s):  
K J Cohen ◽  
J S Hanna ◽  
J E Prescott ◽  
C V Dang
Keyword(s):  
Ring Finger ◽  
Cellular Transformation ◽  
Protein Product ◽  
Polycomb Group ◽  
Wild Type ◽  
Nuclear Entry ◽  
Ring Finger Domain ◽  
Subnuclear Localization ◽  
Transcriptional Suppression

The bmi-1 oncogene cooperates with c-myc in transgenic mice, resulting in accelerated lymphoma development. Altering the expression of Bmi-1 affects normal embryogenesis. The protein product of bmi-1 is homologous to certain Drosophila Polycomb group proteins that regulate homeotic gene expression through alteration of chromatin structure. Chimeric LexA-Bmi-1 protein has previously been shown to repress transcription. How Bmi-1 functions in embryogenesis and whether this relates to the ability of Bmi-1 to mediate cellular transformation is unknown. We demonstrate here that Bmi-1 is able to transform rodent fibroblasts in vitro, providing a system that has allowed us to correlate its molecular properties with its ability to transform cells. We map functional domains of Bmi-1 involved in transcriptional suppression by using the GAL4 chimeric transcriptional regulator system. Deletion analysis shows that the centrally located helix-turn-helix-turn-helix-turn (HTHTHT) motif is necessary for transcriptional suppression whereas the N-terminal RING finger domain is not required. We demonstrate that nuclear localization requires KRMK (residues 230 to 233) and that the absence of nuclear entry ablates transformation. In addition, we find that the subnuclear localization of wild-type Bmi-1 to the rim of the nucleus requires the RING finger domain and correlates with its ability to transform. Our studies with Bmi-1 deletion mutants suggest that the ability of Bmi-1 to mediate cellular transformation correlates with its unique subnuclear localization but not its transcriptional suppression activity.

scholarly journals MEKK1 Mediates the Ubiquitination and Degradation of c-Jun in Response to Osmotic Stress

2006 ◽  
Vol 27 (2) ◽  
pp. 510-517 ◽  
Author(s):  
Yan Xia ◽  
Ji Wang ◽  
Shuichan Xu ◽  
Gary L. Johnson ◽  
Tony Hunter ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
Opposite Effect ◽  
Ring Finger ◽  
Regulatory Proteins ◽  
Wild Type ◽  
Ring Finger Domain ◽  
Ubiquitin Ligase Activity ◽  
Exogenous Expression

ABSTRACT c-Jun, a major transcription factor in the activating protein 1 family of regulatory proteins, is activated by many physiologic and pathological stimuli. We show here that c-Jun was downregulated in response to osmotic stress via ubiquitination-dependent degradation by the PHD/RING finger domain of MEKK1, which exhibited E3 ubiquitin ligase activity toward c-Jun in vitro and in vivo. The reduced c-Jun protein level resulting from exogenous expression of wild-type MEKK1 and the opposite effect induced by expression of a MEKK1 PHD/RING finger domain mutant were consistent with a higher level of c-Jun protein in MEKK1−/− cells than in corresponding wild-type cells. The deficiency of MEKK1 blocked posttranslational downregulation of c-Jun in response to osmotic stress. Furthermore, apoptosis induced by osmotic stress was suppressed by overexpression of c-Jun, indicating that the downregulation of c-Jun promotes apoptosis.

scholarly journals Integrase Mediates Nuclear Localization of Ty3

2001 ◽  
Vol 21 (22) ◽  
pp. 7826-7838 ◽  
Author(s):  
Sophia S. Lin ◽  
M. Henrietta Nymark-McMahon ◽  
Lynn Yieh ◽  
Suzanne B. Sandmeyer
Keyword(s):  
Nuclear Localization ◽  
Transcription Initiation ◽  
Fluorescent Protein ◽  
Rna Polymerase Iii ◽  
Trna Genes ◽  
Nuclear Entry ◽  
Subnuclear Localization ◽  
Viruslike Particles ◽  
Green Fluorescent

ABSTRACT Retroviruses in nondividing cells and yeast retrotransposons must transit the nuclear membrane in order for integration to occur. Mutations in a bipartite basic motif in the carboxyl-terminal domain of the Ty3 integrase (IN) protein were previously shown to block transposition at a step subsequent to 3′-end processing of Ty3 extrachromosomal DNA. In this work, the Ty3 IN was shown to be sufficient to target green fluorescent protein to the nucleolus. Mutations in the bipartite basic motif abrogated this localization. The region containing the motif was shown to be sufficient for nuclear but not subnuclear localization of a heterologous protein. Viruslike particles (VLPs) from cells expressing a Ty3 element defective for nuclear localization were inactive in an in vitro integration assay, suggesting that nuclear entry is required to form active VLPs or that this motif is required for post-nuclear entry steps. Ty3 inserts at transcription initiation sites of genomic tRNA genes and plasmid-borne 5S and U6 RNA genes transcribed by RNA polymerase III. In situ hybridization with Ty3- and Ty3 long terminal repeat-specific probes showed that these elements which are associated with tRNA genes do not colocalize with the ribosomal DNA (rDNA). However, a PCR assay of cells undergoing transposition showed that Ty3 insertion does occur into the 5S genes, which, in yeast, are interspersed with the rDNA and therefore, like Ty3 IN, associated with the nucleolus.

Sec59 encodes a membrane protein required for core glycosylation in Saccharomyces cerevisiae

1989 ◽  
Vol 9 (3) ◽  
pp. 1191-1199
Author(s):  
M Bernstein ◽  
F Kepes ◽  
R Schekman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Product ◽  
Carboxypeptidase Y ◽  
Secretory Proteins ◽  
Restrictive Temperature ◽  
Wild Type ◽  
Partial Restoration ◽  
Alpha Factor ◽  
Mutant Cells

When incubated at a restrictive temperature, Saccharomyces cerevisiae sec59 mutant cells accumulate inactive and incompletely glycosylated forms of secretory proteins. Three different secretory polypeptides (invertase, pro-alpha-factor, and pro-carboxypeptidase Y) accumulated within a membrane-bounded organelle, presumably the endoplasmic reticulum, and resisted proteolytic degradation unless the membrane was permeabilized with detergent. Molecular cloning and DNA sequence analysis of the SEC59 gene predicted an extremely hydrophobic protein product of 59 kilodaltons. This prediction was confirmed by reconstitution of the sec59 defect in vitro. The alpha-factor precursor, which was translated in a soluble fraction from wild-type cells, was translocated into, but inefficiently glycosylated within, membranes from sec59 mutant cells. Residual glycosylation activity of membranes of sec59 cells was thermolabile compared with the activity of wild-type membranes. Partial restoration of glycosylation was obtained in reactions that were supplemented with mannose or GDP-mannose, but not those supplemented with other sugar nucleotides. These results were consistent with a role for the Sec59 protein in the transfer of mannose to dolichol-linked oligosaccharide.

scholarly journals P01.29 Mutant (R132H) IDH1-driven cellular transformation makes cells dependent on continued wild type IDH1 expression in a model of in vitro gliomagenesis

2017 ◽  
Vol 19 (suppl_3) ◽  
pp. iii29-iii30
Author(s):  
T. Johannessen ◽  
J. Mukherjee ◽  
M. Wood ◽  
P. Viswanath ◽  
S. Ohba ◽  
...  
Keyword(s):  
Cellular Transformation ◽  
Wild Type

scholarly journals The checkpoint protein Chfr is a ligase that ubiquitinates Plk1 and inhibits Cdc2 at the G2 to M transition

2002 ◽  
Vol 156 (2) ◽  
pp. 249-260 ◽  
Author(s):  
Dongmin Kang ◽  
James Chen ◽  
Jim Wong ◽  
Guowei Fang
Keyword(s):  
Ring Finger ◽  
Cdc2 Kinase ◽  
Ring Finger Domain ◽  
Checkpoint Protein ◽  
Checkpoint Pathway ◽  
Dependent Protein ◽  
Wee1 Kinase ◽  
Mitotic Stress

The checkpoint protein Chfr delays entry into mitosis, in the presence of mitotic stress (Scolnick, D.M., and T.D. Halazonetis. 2000. Nature. 406:430–435). We show here that Chfr is a ubiquitin ligase, both in vitro and in vivo. When transfected into HEK293T cells, Myc–Chfr promotes the formation of high molecular weight ubiquitin conjugates. The ring finger domain in Chfr is required for the ligase activity; this domain auto-ubiquitinates, and mutations of conserved residues in this domain abolish the ligase activity. Using Xenopus cell-free extracts, we demonstrated that Chfr delays the entry into mitosis by negatively regulating the activation of the Cdc2 kinase at the G2–M transition. Specifically, the Chfr pathway prolongs the phosphorylated state of tyrosine 15 in Cdc2. The Chfr-mediated cell cycle delay requires ubiquitin-dependent protein degradation, because inactivating mutations in Chfr, interference with poly-ubiquitination, and inhibition of proteasomes all abolish this delay in mitotic entry. The direct target of the Chfr pathway is Polo-like kinase 1 (Plk1). Ubiquitination of Plk1 by Chfr delays the activation of the Cdc25C phosphatase and the inactivation of the Wee1 kinase, leading to a delay in Cdc2 activation. Thus, the Chfr pathway represents a novel checkpoint pathway that regulates the entry into mitosis by ubiquitin-dependent proteolysis.

scholarly journals Identification of Three New Genes Involved in Morphogenesis and Antibiotic Production in Streptomyces coelicolor

2003 ◽  
Vol 185 (20) ◽  
pp. 6147-6157 ◽  
Author(s):  
Ondrej Sprusansky ◽  
Liqin Zhou ◽  
Sarah Jordan ◽  
Jared White ◽  
Janet Westpheling
Keyword(s):  
Antibiotic Production ◽  
Streptomyces Coelicolor ◽  
Transcriptional Regulators ◽  
Protein Product ◽  
In Vitro Mutagenesis ◽  
Wild Type ◽  
Prolonged Incubation ◽  
New Genes ◽  
Rich Media

ABSTRACT We report the isolation and partial characterization of three new mutants of Streptomyces coelicolor that are defective in morphogenesis and antibiotic production. The genes identified by the mutations were located and cloned by using a combination of Tn5 in vitro mutagenesis, cotransformation, and genetic complementation. Mutant SE69 produces lower amounts of antibiotics than the wild type produces, produces spores only after prolonged incubation on rich media, and identifies a gene whose predicted protein product is similar to the GntR family of transcriptional regulators; also, production of aerial mycelia on both rich and poor media is significantly delayed in this mutant. Mutant SE293 is defective in morphogenesis, overproduces antibiotics on rich media, fails to grow on minimal media, and identifies a gene whose predicted protein product is similar to the TetR family of transcriptional regulators. Preliminary evidence suggests that the SE293 gene product may control a molybdopterin binding protein located immediately adjacent to it. Mutant SJ175 sporulates sooner and more abundantly than the wild type and overproduces antibiotics on rich media, and it identifies a gene whose predicted protein product contains regions of predominantly hydrophobic residues similar to those of integral membrane proteins.

scholarly journals Sec59 encodes a membrane protein required for core glycosylation in Saccharomyces cerevisiae.

1989 ◽  
Vol 9 (3) ◽  
pp. 1191-1199 ◽  
Author(s):  
M Bernstein ◽  
F Kepes ◽  
R Schekman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Product ◽  
Carboxypeptidase Y ◽  
Secretory Proteins ◽  
Restrictive Temperature ◽  
Wild Type ◽  
Partial Restoration ◽  
Alpha Factor ◽  
Mutant Cells

When incubated at a restrictive temperature, Saccharomyces cerevisiae sec59 mutant cells accumulate inactive and incompletely glycosylated forms of secretory proteins. Three different secretory polypeptides (invertase, pro-alpha-factor, and pro-carboxypeptidase Y) accumulated within a membrane-bounded organelle, presumably the endoplasmic reticulum, and resisted proteolytic degradation unless the membrane was permeabilized with detergent. Molecular cloning and DNA sequence analysis of the SEC59 gene predicted an extremely hydrophobic protein product of 59 kilodaltons. This prediction was confirmed by reconstitution of the sec59 defect in vitro. The alpha-factor precursor, which was translated in a soluble fraction from wild-type cells, was translocated into, but inefficiently glycosylated within, membranes from sec59 mutant cells. Residual glycosylation activity of membranes of sec59 cells was thermolabile compared with the activity of wild-type membranes. Partial restoration of glycosylation was obtained in reactions that were supplemented with mannose or GDP-mannose, but not those supplemented with other sugar nucleotides. These results were consistent with a role for the Sec59 protein in the transfer of mannose to dolichol-linked oligosaccharide.

scholarly journals Knockdown of Polycomb-Group RING Finger 6 Modulates Mouse Male Germ Cell Differentiation in Vitro

2015 ◽  
Vol 35 (1) ◽  
pp. 339-352 ◽  
Author(s):  
Jin Sun ◽  
Jian Wang ◽  
Lin He ◽  
Yi Lin ◽  
Ji Wu
Keyword(s):  
Germ Cell ◽  
Group Ring ◽  
Cellular Localization ◽  
Promoter Activity ◽  
Ring Finger ◽  
Polycomb Group ◽  
Male Germ Cell ◽  
Luciferase Reporter ◽  
Germ Cell Differentiation

Background: Polycomb-group RING finger 6 (PCGF6), one of six PCGF homologs, is the core component of the PRC1 complex that plays critical roles in epigenetic transcriptional silencing in higher eukaryotes. However, the biological functions of PCGF6 are unknown. Method: qRT-PCR and Western blot were used to detect the expression profile of PCGF6 in testes. Fluorescent immunohistochemistry was used to examine the cellular localization of PCGF6 protein in testes. Cell proliferation was tested by performing CCK-8 and EdU incorporation assay. Cell cycle and haploid cell population analysis was determined by flow cytometry using propidium iodide DNA staining. Co-immunoprecipitation experiment was conducted using PCGF6 antibody to obtain interacting protein of PCGF6. Luciferase reporter assays were performed to examine the promoter activity of PCGF6 in cells overexpressing OVOL1 and PLZF. Results: PCGF6 was expressed predominantly in meiotic and post-meiotic male germ cells, could negatively regulate the proliferation of GC-2 spd cells, an immortalized mouse spermatogenic cell line, and could modulate the differentiation of GC-2 spd cells in vitro. PCGF6 could indirectly interact with HSPA2, a key factor that is essential for male meiosis, and OVOL1 and PLZF, two key transcription factors that are involved in spermatogenesis, could positively and negatively modulate Pcgf6 promoter activity, respectively. PCGF1, BMI1, and PCGF5 are also highly expressed in mouse testes like PCGF6. Conclusion: PCGF6 may play important roles in male germ cell development.

Characterization Of In Vitro Hdm2 E3 Ubiquitin Ligase-Mediated p53 Ubiquitination

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4903-4903
Author(s):  
Bradley B Brasher ◽  
Eduardo Guillen ◽  
Ivan Tomasic ◽  
Carsten Schwerdtfeger ◽  
Francesco D Melandri
Keyword(s):  
Transcriptional Activation ◽  
Cell Function ◽  
Ring Finger ◽  
Ubiquitin Ligases ◽  
Wild Type ◽  
Western Blots ◽  
Hematopoietic Stem ◽  
In Vivo Experiments

Abstract Double minute 2 protein (Mdm2, Hdm2 in humans) is a RING-finger Ubiquitin E3 Ligase that acts as a major regulator of the tumor suppressor protein p53. Mdm2 inhibits p53 -mediated cell cycle arrest and apoptosis by binding its transcriptional activation domain. The ligase activity of Mdm2 is responsible for the ubiquitination and subsequent proteasomal degradation of p53. Mdm2 also regulates its own intracellular levels by auto-ubiquitination, and can be SUMOylated, which reportedly decreases autoubiquitination activity but increases activity toward p53. Imbalances in the p53 pathway are frequently associated with hematologic disease states. Loss of p53 function is a driving force in leukemia and lymphoma in humans and mice, while increased p53 activity can inhibit hematopoietic stem cell function and contribute to myelodysplasia. Thus, careful control of p53 activity is critical for homeostasis. Most of our understanding of p53 function in hematopoiesis is derived from in vivo experiments using genetically modified mice (Pant V., et al, Blood. 2012; 120:5118-27). While this is a powerful system for elucidating genetic pathways that influence p53 activity, there is still much to learn about the mechanisms of p53 regulation at the enzymatic level. To facilitate studies in this area, we purified recombinant Hdm2 and p53 from E.coli and developed gel-based assays to monitor both autoubiquitination and ubiquitination of protein substrates. We observed rapid autoubiquitination of Hdm2 using both wild-type and lysine-less (K0) ubiquitin, though reactions containing the former generated significantly higher molecular weight Hdm2-ubiquitin adducts. Hdm2 ubiquitination of p53 produced a discrete, ladder-like banding pattern on Western Blots regardless of whether wild-type or K0 ubiquitin was included in the reaction. This suggests that the principal product of this defined Hdm2-p53 reaction is multi-monoubiquitinated p53, as opposed to p53 modified with polyubiquitin chains. Reactions using an alternative substrate yielded different results. Hdm2 ubiquitination of Angiocidin/S5a protein generated a large smeary pattern on Western Blots instead of discrete bands. This is consistent with the Hdm2-catalyzed polyubiquitination of S5a, demonstrating that ubiquitin ligases are capable of generating different in vitro ubiquitination patterns that are dependent on the substrate utilized in the assay. These results suggest that care must be taken in experimental designs, particularly with respect to substrate and assay read out. Finally, recombinant UBE4B was included in Mdm2/p53 reactions to test the recently reported E4-ligase activity of this enzyme. Ultimately these reagents should prove useful for fully defined, in vitro studies investigating the interactions between p53 and the ubiquitin ligases and deubiquitinases that modify it in normal and diseased cellular states. Disclosures: Brasher: Boston Biochem Inc: Employment. Guillen:Boston Biochem Inc: Employment. Tomasic:Boston Biochem Inc: Employment. Schwerdtfeger:Boston Biochem Inc: Employment. Melandri:Boston Biochem Inc: Employment.

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