February 7th, 2010 / No Comments » / by Carrassa L, Sanchez Y, Erba E, Damia G
U2OS cells lacking Chk1 undergo aberrant mitosis and fail to activate the spindle checkpoint.
J Cell Mol Med. 2009 Aug;13(8A):1565-76
Authors: Carrassa L, Sanchez Y, Erba E, Damia G
Chk1 is a conserved protein kinase originally identified in fission yeast, required to delay entry of cells with damaged or unreplicated DNA into mitosis. The requirement of Chk1 for both S and G2/M checkpoints has been elucidated while only few studies have connected Chk1 to the mitotic spindle checkpoint. We used a small interference RNA strategy to investigate the role of Chk1 in unstressed conditions. Chk1 depletion in U2OS human osteosarcoma cells inhibited cell proliferation and raised the percentage of cells with a 4N DNA content, which correlated with accumulation of giant polynucleated cells morphologically distinct from apoptotic cells, while no increased number of cells in G2 or mitosis could be detected. Down-regulation of Chk1 also caused accumulation of cells in the last step of cytokinesis, and of tetraploid cells in G1 phase, which coincided with activation of p53 and increased levels of p21. In addition, Chk1-depleted U2OS cells failed to arrest in mitosis after spindle disruption by nocodazole and showed decreased protein levels of Mad2 and BubR1. These studies show that U2OS cells lacking Chk1 undergo abnormal mitosis and fail to activate the spindle checkpoint, suggesting a role of Chk1 in this checkpoint.
PMID: 19778378 [PubMed - indexed for MEDLINE]
Posted in: J Cell Mol Med
February 7th, 2010 / No Comments » / by Zhang D, Chen T, Ziv I, Rosenzweig R, Matiuhin Y, Bronner V, Glickman MH, Fushman D
Together, Rpn10 and Dsk2 can serve as a polyubiquitin chain-length sensor.
Mol Cell. 2009 Dec 25;36(6):1018-33
Authors: Zhang D, Chen T, Ziv I, Rosenzweig R, Matiuhin Y, Bronner V, Glickman MH, Fushman D
As a signal for substrate targeting, polyubiquitin meets various layers of receptors upstream to the 26S proteasome. We obtained structural information on two receptors, Rpn10 and Dsk2, alone and in complex with (poly)ubiquitin or with each other. A hierarchy of affinities emerges with Dsk2 binding monoubiquitin tighter than Rpn10 does, whereas Rpn10 prefers the ubiquitin-like domain of Dsk2 to monoubiquitin, with increasing affinities for longer polyubiquitin chains. We demonstrated the formation of ternary complexes of both receptors simultaneously with (poly)ubiquitin and found that, depending on the ubiquitin chain length, the orientation of the resulting complex is entirely different, providing for alternate signals. Dynamic rearrangement provides a chain-length sensor, possibly explaining how accessibility of Dsk2 to the proteasome is limited unless it carries a properly tagged cargo. We propose a mechanism for a malleable ubiquitin signal that depends both on chain length and combination of receptors to produce tetraubiquitin as an efficient signal threshold.
PMID: 20064467 [PubMed - indexed for MEDLINE]
Posted in: Mol Cell
February 7th, 2010 / No Comments » / by Popova Y, Thayumanavan P, Lonati E, Agrochão M, Thevelein JM
Transport and signaling through the phosphate-binding site of the yeast Pho84 phosphate transceptor.
Proc Natl Acad Sci U S A. 2010 Feb 1;
Authors: Popova Y, Thayumanavan P, Lonati E, Agrochão M, Thevelein JM
A novel concept in eukaryotic signal transduction is the use of nutrient transporters and closely related proteins as nutrient sensors. The action mechanism of these "transceptors" is unclear. The Pho84 phosphate transceptor in yeast transports phosphate and mediates rapid phosphate activation of the protein kinase A (PKA) pathway during growth induction. We have now identified several phosphate-containing compounds that act as nontransported signaling agonists of Pho84. This indicates that signaling does not require complete transport of the substrate. For the nontransported agonist glycerol-3-phosphate (Gly3P), we show that it is transported by two other carriers, Git1 and Pho91, without triggering signaling. Gly3P is a competitive inhibitor of transport through Pho84, indicating direct interaction with its phosphate-binding site. We also identified phosphonoacetic acid as a competitive inhibitor of transport without agonist function for signaling. This indicates that binding of a compound into the phosphate-binding site of Pho84 is not enough to trigger signaling. Apparently, signaling requires a specific conformational change that may be part of, but does not require, the complete transport cycle. Using Substituted Cysteine Accessibility Method (SCAM) we identified Phe(160) in TMD IV and Val(392) in TMD VIII as residues exposed with their side chain into the phosphate-binding site of Pho84. Inhibition of both transport and signaling by covalent modification of Pho84(F160C) or Pho84(V392C) showed that the same binding site is used for transport of phosphate and for signaling with both phosphate and Gly3P. Our results provide to the best of our knowledge the first insight into the molecular mechanism of a phosphate transceptor.
PMID: 20133652 [PubMed - as supplied by publisher]
Posted in: Proc Natl Acad Sci U S A
February 7th, 2010 / No Comments » / by Nigam N, George J, Srivastava S, Roy P, Bhui K, Singh M, Shukla Y
Induction of apoptosis by [6]-gingerol associated with the modulation of p53 and involvement of mitochondrial signaling pathway in B[a]P-induced mouse skin tumorigenesis.
Cancer Chemother Pharmacol. 2010 Mar;65(4):687-96
Authors: Nigam N, George J, Srivastava S, Roy P, Bhui K, Singh M, Shukla Y
PURPOSE: To unravel the molecular mechanisms underlying the chemopreventive potential of [6]-gingerol, a pungent ingredient of ginger rhizome (Zingiber officinale Roscoe, Zingiberaceae), against benzo[a]pyrene (B[a]P)-induced mouse skin tumorigenesis. METHODS: Topical treatment of [6]-gingerol (2.5 muM/animal) was given to the animals 30 min prior and post to B[a]P (5 mug/animal) for 32 weeks. At the end of the study period, the skin tumors/tissues were dissected out and examined histopathologically. Flow cytometry was employed for cell cycle analysis. Further immunohistochemical localization of p53 and regulation of related apoptogenic proteins were determined by Western blotting. RESULTS: Chemopreventive properties of [6]-gingerol were reflected by delay in onset of tumorigenesis, reduced cumulative number of tumors, and reduction in tumor volume. Cell cycle analysis revealed that the appearance of sub-G1 peak was significantly elevated in [6]-gingerol treated animals with post treatment showing higher efficacy in preventing tumorigenesis induced by B[a]P. Moreover, elevated apoptotic propensity was observed in tumor tissues than the corresponding non-tumor tissues. Western blot analysis also showed the same pattern of chemoprevention with [6]-gingerol treatment increasing the B[a]P suppressed p53 levels, also evident by immunohistochemistry, and Bax while decreasing the expression of Bcl-2 and Survivin. Further, [6]-gingerol treatment resulted in release of Cytochrome c, Caspases activation, increase in apoptotic protease-activating factor-1 (Apaf-1) as mechanism of apoptosis induction. CONCLUSIONS: On the basis of the results we conclude that [6]-gingerol possesses apoptotic potential in mouse skin tumors as mechanism of chemoprevention hence deserves further investigation.
PMID: 19629484 [PubMed - indexed for MEDLINE]
Posted in: Cancer Chemother Pharmacol
February 7th, 2010 / No Comments » / by Bredholt T, Dimba EA, Hagland HR, Wergeland L, Skavland J, Fossan KO, Tronstad KJ, Johannessen AC, Vintermyr OK, Gjertsen BT
Camptothecin and khat (Catha edulis Forsk.) induced distinct cell death phenotypes involving modulation of c-FLIPL, Mcl-1, procaspase-8 and mitochondrial function in acute myeloid leukemia cell lines.
Mol Cancer. 2009;8:101
Authors: Bredholt T, Dimba EA, Hagland HR, Wergeland L, Skavland J, Fossan KO, Tronstad KJ, Johannessen AC, Vintermyr OK, Gjertsen BT
BACKGROUND: An organic extract of the recreational herb khat (Catha edulis Forsk.) triggers cell death in various leukemia cell lines in vitro. The chemotherapeutics camptothecin, a plant alkaloid topoisomerase I inhibitor, was tested side-by-side with khat in a panel of acute myeloid leukemia cell lines to elucidate mechanisms of toxicity. RESULTS: Khat had a profound effect on MOLM-13 cells inducing mitochondrial damage, chromatin margination and morphological features of autophagy. The effects of khat on mitochondrial ultrastructure in MOLM-13 correlated with strongly impaired routine respiration, an effect neither found in the khat-resistant MV-4-11 cells nor in camptothecin treated cells. Enforced expression of anti-apoptotic Bcl-2 protein provided protection against camptothecin-induced cell death and partly against khat toxicity. Khat-induced cell death in MOLM-13 cells included reduced levels of anti-apoptotic Mcl-1 protein, while both khat and camptothecin induced c-FLIPL cleavage and procaspase-8 activation. CONCLUSION: Khat activated a distinct cell death pathway in sensitive leukemic cells as compared to camptothecin, involving mitochondrial damage and morphological features of autophagy. This suggests that khat should be further explored in the search for novel experimental therapeutics.
PMID: 19912650 [PubMed - indexed for MEDLINE]
Posted in: Mol Cancer
February 6th, 2010 / No Comments » / by Lindemann CB
Heart of the beat (the flagellar beat, that is).
Biophys J. 2009 Dec 2;97(11):2865-6
Authors: Lindemann CB
PMID: 19948114 [PubMed - indexed for MEDLINE]
Posted in: Biophys J
February 6th, 2010 / No Comments » / by pubmed
153 new pubmed citations were retrieved for your search.
Click on the search hyperlink below to display the complete search results:
kinase
These pubmed results were generated on 2010/02/06
PubMed, a service of the National Library of Medicine, includes over 15 million
citations for biomedical articles back to the 1950's.
These citations are from MEDLINE and additional life science journals.
PubMed includes links to many sites providing full text articles and other related resources.
Posted in: Report
February 6th, 2010 / No Comments » / by Ho AK, Chik CL
Modulation of Aanat gene transcription in the rat pineal gland.
J Neurochem. 2010 Jan;112(2):321-31
Authors: Ho AK, Chik CL
The main function of the rat pineal gland is to transform the circadian rhythm generated in the suprachiasmatic nucleus into a rhythmic signal of circulating melatonin characterized by a large nocturnal increase that closely reflects the duration of night period. This is achieved through the tight coupling between environmental lighting and the expression of arylalkylamine-N-acetyltransferase, the rhythm-controlling enzyme in melatonin synthesis. The initiation of Aanat transcription at night is controlled largely by the norepinephrine-stimulated phosphorylation of cAMP response element-binding protein by protein kinase A. However, to accurately reflect the duration of darkness, additional signaling mechanisms also participate to fine-tune the temporal profile of adrenergic-induced Aanat transcription. Here, we reviewed some of these signaling mechanisms, with emphasis on the more recent findings. These signaling mechanisms can be divided into two groups: those involving modification of constitutively expressed proteins and those requiring synthesis of new proteins. This review highlights the pineal gland as an excellent model system for studying neurotransmitter-regulated rhythmic gene expression.
PMID: 19860854 [PubMed - indexed for MEDLINE]
Posted in: J Neurochem
February 6th, 2010 / No Comments » / by Thorp MW, Chapman EJ, Simmons MJ
Cytotype regulation by telomeric P elements in Drosophila melanogaster: variation in regulatory strength and maternal effects.
Genet Res. 2009 Oct;91(5):327-36
Authors: Thorp MW, Chapman EJ, Simmons MJ
Strains carrying the X-linked telomeric P elements TP5 or TP6 varied in their ability to repress hybrid dysgenesis. The rank ordering of these strains was consistent across different genetic assays and was not related to the type of telomeric P element (TP5 or TP6) present. Strong repression of dysgenesis was associated with weak expression of mRNA from the telomeric P element and also with a reduced amount of mRNA from a transposase-producing P element contained within a transgene inserted on an autosome. A strictly maternal component of repression, transmitted independently of the telomeric P element, was detected in the daughters but not the sons of females from the strongest repressing strains. However, this effect was seen only when dysgenesis was induced by crossing these females to males from a P strain, not when it was induced by crossing them to males homozygous for a single transposase-producing P element contained within a transgene. These findings are consistent with the hypothesis that the P cytotype, the condition that regulates P elements, involves an RNA interference mechanism mediated by piRNAs produced by telomeric P elements such as TP5 and TP6 and amplified by RNAs produced by other P elements.
PMID: 19922696 [PubMed - indexed for MEDLINE]
Posted in: Genet Res
February 6th, 2010 / No Comments » / by pubmed
21 new pubmed citations were retrieved for your search.
Click on the search hyperlink below to display the complete search results:
autoimmune
These pubmed results were generated on 2010/02/06
PubMed, a service of the National Library of Medicine, includes over 15 million
citations for biomedical articles back to the 1950's.
These citations are from MEDLINE and additional life science journals.
PubMed includes links to many sites providing full text articles and other related resources.
Posted in: Report
