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  • Distinct mechanisms are utilized to induce stress sensor gadd45b by different stress stimuli. 19834918

    The GADD45 family of proteins consists of three small proteins, GADD45A, GADD45B, and GADD45G, implicated in modulating the cellular response to genotoxic/physiological stressors. Despite similarities in sequence, structure and function, each gadd45 gene is induced differentially by different stress stimuli. Studies on stress-mediated induction of the gadd45 genes have predominantly focused on gadd45a, with knowledge of gadd45b and gadd45g regulation lacking. To generate a more complete understanding of the regulation of gadd45 genes, a comprehensive analysis of stress-mediated induction of human gadd45b has been carried out using human RKO colorectal carcinoma cells as a model system. Novel data indicate that gadd45b induction in RKO cells is regulated by distinct mechanisms in a stress-specific manner. Methylmethane sulfonate (MMS), a DNA alkylating agent, induces gadd45b transcription through a cohort of both constitutive and inducible bound factors, including NFY, Sp1 and Egr1. In contrast, in a hyperosmotic environment generated with sorbitol, gadd45b mRNA is induced exclusively by mRNA stabilization. These findings indicate that the stress-mediated induction of gadd45b is largely distinct from gadd45a. Furthermore, data obtained provide a novel paradigm for stress-response gene induction, indicating that gadd45b induction by distinct stressors, in the same cell type and under the same experimental settings, is differentially regulated at the level of mRNA transcription or mRNA stability. Importantly, this study also provides the groundwork to further examine the regulation of gadd45b expression in in vivo settings using animal models and tissues obtained from normal individuals and cancer patients prior to and after chemotherapeutic intervention.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    17-371
    Produktbezeichnung:
    EZ-ChIP™

  • Role of spleen-derived monocytes/macrophages in acute ischemic brain injury. 24865998

    Monocytes/macrophages (MMs), mononuclear phagocytes, have been implicated in stroke-induced inflammation and injury. However, the presence of pro-inflammatory Ly-6C(high) and antiinflammatory Ly-6C(low) monocyte subsets raises uncertainty regarding their role in stroke pathologic assessment. With recent identification of the spleen as an immediate reservoir of MMs, this current study addresses whether the spleen-derived MMs are required for stroke pathologic assessment. We observed that the spleen was contracted in poststroke animals and the contraction was accompanied by decreased number of Ly-6C(high) and Ly-6C(low) subsets in the spleen. The deployment of these subsets from the spleen temporally coincided with respective increases in the ischemic brain. Compared to mice with the spleen, mice receiving a splenectomy just before the stroke displayed less accumulation of Ly-6C(high) and Ly-6C(low) MMs in the brain. Despite the reduced accumulation of both subsets, infarct size and swelling were not reduced in the asplenic mice. The dissociative findings of infarct size and extent of MM infiltration in the postischemic brain indicate minimal involvement of spleen-derived total MMs in acute infarct development. Selective Ly-6C(high) or Ly-6C(low) MM targeting is suggested to address the contribution of the individual subset to acute stroke pathologic assessment.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    Mehrere
    Produktbezeichnung:
    Mehrere

  • Roles of PCNA ubiquitination and TLS polymerases κ and η in the bypass of methyl methanesulfonate-induced DNA damage. 25505145

    Translesion synthesis (TLS) provides a highly conserved mechanism that enables DNA synthesis on a damaged template. TLS is performed by specialized DNA polymerases of which polymerase (Pol) κ is important for the cellular response to DNA damage induced by benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), ultraviolet (UV) light and the alkylating agent methyl methanesulfonate (MMS). As TLS polymerases are intrinsically error-prone, tight regulation of their activity is required. One level of control is provided by ubiquitination of the homotrimeric DNA clamp PCNA at lysine residue 164 (PCNA-Ub). We here show that Polκ can function independently of PCNA modification and that Polη can function as a backup during TLS of MMS-induced lesions. Compared to cell lines deficient for PCNA modification (Pcna(K164R)) or Polκ, double mutant cell lines display hypersensitivity to MMS but not to BPDE or UV-C. Double mutant cells also displayed delayed post-replicative TLS, accumulate higher levels of replication stress and delayed S-phase progression. Furthermore, we show that Polη and Polκ are redundant in the DNA damage bypass of MMS-induced DNA damage. Taken together, we provide evidence for PCNA-Ub-independent activation of Polκ and establish Polη as an important backup polymerase in the absence of Polκ in response to MMS-induced DNA damage.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    MAB1501R
    Produktbezeichnung:
    Anti-Actin Antibody,clone C4

  • Schizosaccharomyces pombe Hst4 functions in DNA damage response by regulating histone H3 K56 acetylation. 18344406

    The packaging of eukaryotic DNA into chromatin is likely to be crucial for the maintenance of genomic integrity. Histone acetylation and deacetylation, which alter chromatin accessibility, have been implicated in DNA damage tolerance. Here we show that Schizosaccharomyces pombe Hst4, a homolog of histone deacetylase Sir2, participates in S-phase-specific DNA damage tolerance. Hst4 was essential for the survival of cells exposed to the genotoxic agent methyl methanesulfonate (MMS) as well as for cells lacking components of the DNA damage checkpoint pathway. It was required for the deacetylation of histone H3 core domain residue lysine 56, since a strain with a point mutation of its catalytic domain was unable to deacetylate this residue in vivo. Hst4 regulated the acetylation of H3 K56 and was itself cell cycle regulated. We also show that MMS treatment resulted in increased acetylation of histone H3 lysine 56 in wild-type cells and hst4Delta mutants had constitutively elevated levels of histone H3 K56 acetylation. Interestingly, the level of expression of Hst4 decreased upon MMS treatment, suggesting that the cell regulates access to the site of DNA damage by changing the level of this protein. Furthermore, we find that the phenotypes of both K56Q and K56R mutants of histone H3 were similar to those of hst4Delta mutants, suggesting that proper regulation of histone acetylation is important for DNA integrity. We propose that Hst4 is a deacetylase involved in the restoration of chromatin structure following the S phase of cell cycle and DNA damage response.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    07-677

  • Regulation of p53 in response to DNA damage. 10618704

    Activation of p53 can occur in response to a number of cellular stresses, including DNA damage, hypoxia and nucleotide deprivation. Several forms of DNA damage have been shown to activate p53, including those generated by ionising radiation (IR), radio-mimetic drugs, ultraviolet light (UV) and chemicals such as methyl methane sulfonate (MMS). Under normal conditions, p53 levels are maintained at a low state by virtue of the extremely short-half life of the polypeptide. In addition to this, p53 normally exists in an largely inactive state that is relatively inefficient at binding to DNA and activating transcription. Activation of p53 in response to DNA damage is associated with a rapid increase in its levels and with an increased ability of p53 to bind DNA and mediate transcriptional activation. This then leads to the activation of a number of genes whose products trigger cell-cycle arrest, apoptosis, or DNA repair. Recent work has suggested that this regulation is brought about largely through DNA damage triggering a series of phosphorylation, de-phosphorylation and acetylation events on the p53 polypeptide. Here, we discuss the nature of these modifications, the enzymes that bring them about, and how changes in p53 modification lead to p53 activation.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    04-1083

  • Dual functions of ASCIZ in the DNA base damage response and pulmonary organogenesis. 20975950

    Zn²(+)-finger proteins comprise one of the largest protein superfamilies with diverse biological functions. The ATM substrate Chk2-interacting Zn²(+)-finger protein (ASCIZ; also known as ATMIN and ZNF822) was originally linked to functions in the DNA base damage response and has also been proposed to be an essential cofactor of the ATM kinase. Here we show that absence of ASCIZ leads to p53-independent late-embryonic lethality in mice. Asciz-deficient primary fibroblasts exhibit increased sensitivity to DNA base damaging agents MMS and H2O2, but Asciz deletion knock-down does not affect ATM levels and activation in mouse, chicken, or human cells. Unexpectedly, Asciz-deficient embryos also exhibit severe respiratory tract defects with complete pulmonary agenesis and severe tracheal atresia. Nkx2.1-expressing respiratory precursors are still specified in the absence of ASCIZ, but fail to segregate properly within the ventral foregut, and as a consequence lung buds never form and separation of the trachea from the oesophagus stalls early. Comparison of phenotypes suggests that ASCIZ functions between Wnt2-2b/ß-catenin and FGF10/FGF-receptor 2b signaling pathways in the mesodermal/endodermal crosstalk regulating early respiratory development. We also find that ASCIZ can activate expression of reporter genes via its SQ/TQ-cluster domain in vitro, suggesting that it may exert its developmental functions as a transcription factor. Altogether, the data indicate that, in addition to its role in the DNA base damage response, ASCIZ has separate developmental functions as an essential regulator of respiratory organogenesis.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    Mehrere
    Produktbezeichnung:
    Mehrere

  • Regulation of tolerance to DNA alkylating damage by Dot1 and Rad53 in Saccharomyces cerevisiae. 20674515

    To maintain genomic integrity cells have to respond properly to a variety of exogenous and endogenous factors that produce genome injuries and interfere with DNA replication. DNA integrity checkpoints coordinate this response by slowing cell cycle progression to provide time for the cell to repair the damage, stabilizing replication forks and stimulating DNA repair to restore the original DNA sequence and structure. In addition, there are also mechanisms of damage tolerance, such as translesion synthesis (TLS), which are important for survival after DNA damage. TLS allows replication to continue without removing the damage, but results in a higher frequency of mutagenesis. Here, we investigate the functional contribution of the Dot1 histone methyltransferase and the Rad53 checkpoint kinase to TLS regulation in Saccharomyces cerevisiae. We demonstrate that the Dot1-dependent status of H3K79 methylation modulates the resistance to the alkylating agent MMS, which depends on PCNA ubiquitylation at lysine 164. Strikingkly, either the absence of DOT1, which prevents full activation of Rad53, or the expression of an HA-tagged version of RAD53, which produces low amounts of the kinase, confer increased MMS resistance. However, the dot1Δ rad53-HA double mutant is hypersensitive to MMS and shows barely detectable amounts of activated kinase. Furthermore, moderate overexpression of RAD53 partially suppresses the MMS resistance of dot1Δ. In addition, we show that MMS-treated dot1Δ and rad53-HA cells display increased number of chromosome-associated Rev1 foci. We propose that threshold levels of Rad53 activity exquisitely modulate the tolerance to alkylating damage at least by controlling the abundance of the key TLS factor Rev1 bound to chromatin.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    05-724
    Produktbezeichnung:
    Anti-Myc Tag Antibody, clone 4A6

  • STAT3 and MAPK signaling maintain overexpression of heat shock proteins 90alpha and beta in multiple myeloma cells, which critically contribute to tumor-cell survival. 17003370

    The combined blockade of the IL-6R/STAT3 and the MAPK signaling pathways has been shown to inhibit bone marrow microenvironment (BMM)-mediated survival of multiple myeloma (MM) cells. Here, we identify the molecular chaperones heat shock proteins (Hsp) 90alpha and beta as target genes of both pathways. The siRNA-mediated knockdown of Hsp90 or treatment with the novel Hsp90 inhibitor 17-DMAG attenuated the levels of STAT3 and phospho-ERK and decreased the viability of MM cells. Although knockdown of Hsp90beta-unlike knockdown of Hsp90alpha-was sufficient to induce apoptosis, this effect was strongly increased when both Hsp90s were targeted, indicating a cooperation of both. Given the importance of the BMM for drug resistance and MM-cell survival, apoptosis induced by Hsp90 inhibition was not mitigated in the presence of bone marrow stromal cells, osteoclasts, or endothelial cells. These observations suggest that a positive feedback loop consisting of Hsp90alpha/beta and major signaling pathways supports the survival of MM cells. Finally, in situ overexpression of both Hsp90 proteins was observed in most MMs but not in monoclonal gammopathy of undetermined significance (MGUS) or in normal plasma cells. Our results underpin a role for Hsp90alpha and beta in MM pathogenesis.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    AB3468
    Produktbezeichnung:
    Anti-Heat Shock Protein 90β Antibody

  • Reversal of PCNA ubiquitylation by Ubp10 in Saccharomyces cerevisiae. 22829782

    Regulation of PCNA ubiquitylation plays a key role in the tolerance to DNA damage in eukaryotes. Although the evolutionary conserved mechanism of PCNA ubiquitylation is well understood, the deubiquitylation of ubPCNA remains poorly characterized. Here, we show that the histone H2B(K123) ubiquitin protease Ubp10 also deubiquitylates ubPCNA in Saccharomyces cerevisiae. Our results sustain that Ubp10-dependent deubiquitylation of the sliding clamp PCNA normally takes place during S phase, likely in response to the simple presence of ubPCNA. In agreement with this, we show that Ubp10 forms a complex with PCNA in vivo. Interestingly, we also show that deletion of UBP10 alters in different ways the interaction of PCNA with DNA polymerase ζ-associated protein Rev1 and with accessory subunit Rev7. While deletion of UBP10 enhances PCNA-Rev1 interaction, it decreases significantly Rev7 binding to the sliding clamp. Finally, we report that Ubp10 counteracts Rad18 E3-ubiquitin ligase activity on PCNA at lysine 164 in such a manner that deregulation of Ubp10 expression causes tolerance impairment and MMS hypersensitivity.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    05-724
    Produktbezeichnung:
    Anti-Myc Tag Antibody, clone 4A6

  • MMPs/TIMPs and inflammatory signalling de-regulation in human incisional hernia tissues. 19397782

    BACKGROUND: Incisional hernia is a common and important complication of laparotomies. Epidemiological studies allude to an underlying biological cause, at least in a subset of population. Interest has mainly focused on abnormal collagen metabolism. However, the role played by other determinants of extracellular matrix (ECM) composition is unknown. To date, there are few laboratory studies investigating the importance of biological factors contributing to incisional hernia development. We performed a descriptive tissue-based analysis to elucidate the possible relevance of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in association with local cytokine induction in human incisional hernia tissues. The expression profiles of MMPs, TIMPs and pro-inflammatory cytokine signalling were investigated in aponeurosis and skeletal muscle specimens taken intraoperatively from incisional hernia (n= 10) and control (n= 10) patients. Semiquantitative RT-PCR, zymography and immunoblotting analyses were done. Incisional hernia samples displayed alterations in the microstructure and loss of ECM, as assessed by histological analyses. Moreover, incisional hernia tissues showed increased MMP/TIMP ratios and de-regulated inflammatory signalling (tumor necrosis factor [TNFA] and interleukin [IL]-6 tended to increase, whereas aponeurosis TNFA receptors decreased). The changes were tissue-specific and were detectable at the mRNA and/or protein level. Statistical analyses showed several associations between individual MMPs, TIMPs, interstitial collagens and inflammatory markers. The increment of MMPs in the absence of a counterbalance by TIMPs, together with an ongoing de-regulated inflammatory signalling, may contribute in inducing a functional defect of the ECM network by post-translational mechanisms, which may trigger abdominal wall tissue loss and eventual rupture. The notable TIMP3 protein down-regulation in incisional hernia fascia may be of pathophysiological significance. We conclude that this study may help to pinpoint novel hypotheses of pathogenesis that can lead to a better understanding of the disease and ultimately to improvement in current therapeutic approaches.
    Dokumententyp:
    Referenz
    Produkbestellnummer:
    AB19027
    Produktbezeichnung:
    Anti-ADAM 17 Antibody