PubMed Central (PMC3 - NLM DTD)
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Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).
Mostrando recursos 61 - 80 de 9,978
61.
A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative ActivitiesD? - Clark, Michael G.; Teply, Joseph; Haarer, Brian K.; Viggiano, Susan C.; Sept, David; Amberg, David C.
Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal ?-propeller and...
62.
Phosphorylation of Xenopus Rad1 and Hus1 Defines a Readout for ATR Activation That Is Independent of Claspin and the Rad9 Carboxy TerminusD? - Lupardus, Patrick J.; Cimprich, Karlene A.
The DNA damage checkpoint pathways sense and respond to DNA damage to ensure genomic stability. The ATR kinase is a central regulator of one such pathway and phosphorylates a number of proteins that have roles in cell cycle progression and DNA repair. Using the Xenopus egg extract system, we have investigated regulation of the Rad1/Hus1/Rad9 complex. We show here that phosphorylation of Rad1 and Hus1 occurs in an ATR- and TopBP1-dependent manner on T5 of Rad1 and S219 and T223 of Hus1. Mutation of these sites has no effect on the phosphorylation of Chk1 by ATR. Interestingly, phosphorylation of Rad1...
63.
Uncoupling the Central Spindle-associated Function of the Chromosomal Passenger Complex from Its Role at CentromeresD? - Lens, Susanne M.A.; Rodriguez, Jose A.; Vader, Gerben; Span, Simone W.; Giaccone, Giuseppe; Medema, René H.
Survivin is a component of the chromosomal passenger complex (CPC) that plays a role in maintenance of an active spindle checkpoint and in cytokinesis. To study whether these different functions can be attributed to distinct domains within the Survivin protein, we complemented Survivin-depleted cells with a variety of point- and deletion-mutants of Survivin. We show that an intact baculovirus IAP repeat (BIR) domain is required for proper spindle checkpoint functioning, but dispensable for cytokinesis. In line with this, mutants lacking an intact BIR domain localized normally to the central spindle, but their localization to inner centromeres was severely perturbed. Consequently,...
64.
Assortment of Phosphatidylinositol 3-Kinase ComplexesAtg14p Directs Association of Complex I to the Pre-autophagosomal Structure in Saccharomyces cerevisiae - Obara, Keisuke; Sekito, Takayuki; Ohsumi, Yoshinori
In the yeast Saccharomyces cerevisiae, two similar phosphatidylinositol 3-kinase complexes (complexes I and II) function in distinct biological processes, complex I in autophagy and complex II in the vacuolar protein sorting via endosomes. Atg14p is only integrated into complex I, likely facilitating the function of complex I in autophagy. Deletion analysis of Atg14p revealed that N-terminal region containing the coiled-coil structures was essential and sufficient for autophagy. Atg14p localized to pre-autophagosomal structure (PAS) and vacuolar membranes, whereas Vps38p, a component specific to complex II, localized to endosomes and vacuolar membranes. Vps34p and Vps30p, components shared by the two complexes, localized...
65.
Involvement of Mitochondrial Complex II Defects in Neuronal Death Produced by N-Terminus Fragment of Mutated Huntingtin - Benchoua, Alexandra; Trioulier, Yaël; Zala, Diana; Gaillard, Marie-Claude; Lefort, Nathalie; Dufour, Noelle; Saudou, Frederic; Elalouf, Jean-Marc; Hirsch, Etienne; Hantraye, Philippe; Déglon, Nicole; Brouillet, Emmanuel
Alterations of mitochondrial function may play a central role in neuronal death in Huntington's disease (HD). However, the molecular mechanisms underlying such functional deficits of mitochondria are not elucidated yet. We herein showed that the expression of two important constituents of mitochondrial complex II, the 30-kDa iron-sulfur (Ip) subunit and the 70-kDa FAD (Fp) subunit, was preferentially decreased in the striatum of HD patients compared with controls. We also examined several mitochondrial proteins in striatal neurons that were infected with lentiviral vectors coding for the N-terminus part of huntingtin (Htt) with either a pathological (Htt171-82Q) or physiological (Htt171-19Q) polyglutamine tract....
66.
Versican Mediates Mesenchymal-Epithelial TransitionD? - Sheng, Wang; Wang, Guizhi; La Pierre, David P.; Wen, Jianping; Deng, Zhaoqun; Wong, Chung-Kwun Amy; Lee, Daniel Y.; Yang, Burton B.
Versican is a large extracellular chondroitin sulfate proteoglycan that belongs to the family of lecticans. Alternative splicing of versican generates at least four isoforms named V0, V1, V2, and V3. We show here that ectopic expression of versican V1 isoform induced mesenchymal-epithelial transition (MET) in NIH3T3 fibroblasts, and inhibition of endogenous versican expression abolished the MET in metanephric mesenchyme. MET in NIH3T3 cells was demonstrated by morphological changes and dramatic alterations in both membrane and cytoskeleton architecture. Molecular analysis showed that V1 promoted a switch in cadherin expression from N- to E-cadherin, resulting in epithelial specific adhesion junctions. V1 expression...
67.
Zonula Occludens-1 Function in the Assembly of Tight Junctions in Madin-Darby Canine Kidney Epithelial CellsD?V? - McNeil, Elizabeth; Capaldo, Christopher T.; Macara, Ian G.
Zonula occludens (ZO)-1 was the first tight junction protein to be cloned and has been implicated as an important scaffold protein. It contains multiple domains that bind a diverse set of junction proteins. However, the molecular functions of ZO-1 and related proteins such as ZO-2 and ZO-3 have remained unclear. We now show that gene silencing of ZO-1 causes a delay of ?3 h in tight junction formation in Madin-Darby canine kidney (MDCK) epithelial cells, but mature junctions seem functionally normal even in the continuing absence of ZO-1. Depletion of ZO-2, cingulin, or occludin, proteins that can interact with ZO-1,...
68.
Rgf1p Is a Specific Rho1-GEF That Coordinates Cell Polarization with Cell Wall Biogenesis in Fission Yeast - García, Patricia; Tajadura, Virginia; García, Ignacio; Sánchez, Yolanda
Rho1p regulates cell integrity by controlling the actin cytoskeleton and cell wall synthesis. We have identified a new GEF, designated Rgf1p, which specifically regulates Rho1p during polarized growth. The phenotype of rgf1 null cells was very similar to that seen after depletion of Rho1p, 30% of cells being lysed. In addition, rgf1+ deletion caused hypersensitivity to the antifungal drug Caspofungin and defects in the establishment of bipolar growth. rho1+, but none of the other GTPases of the Rho-family, suppressed the rgf1? phenotypes. Moreover, deletion of rgf1+ suppressed the severe growth defect in rga1+ null mutants (a Rho1-GAP, negative regulator). Rgf1p...
69.
Senescence of Human Fibroblasts after Psoralen Photoactivation Is Mediated by ATR Kinase and Persistent DNA Damage Foci at TelomeresD? - Hovest, Miriam Grosse; Brüggenolte, Nicole; Hosseini, Kijawasch Shah; Krieg, Thomas; Herrmann, Gernot
Cellular senescence is a phenotype that is likely linked with aging. Recent concepts view different forms of senescence as permanently maintained DNA damage responses partially characterized by the presence of senescence-associated DNA damage foci at dysfunctional telomeres. Irradiation of primary human dermal fibroblasts with the photosensitizer 8-methoxypsoralen and ultraviolet A radiation (PUVA) induces senescence. In the present study, we demonstrate that senescence after PUVA depends on DNA interstrand cross-link (ICL) formation that activates ATR kinase. ATR is necessary for the manifestation and maintenance of the senescent phenotype, because depletion of ATR expression before PUVA prevents induction of senescence, and reduction...
70.
PARP1 Is a TRF2-associated Poly(ADP-Ribose)Polymerase and Protects Eroded TelomeresD? - Gomez, Marla; Wu, Jun; Schreiber, Valérie; Dunlap, John; Dantzer, Françoise; Wang, Yisong; Liu, Yie
Poly(ADP-ribose)polymerase 1 (PARP1) is well characterized for its role in base excision repair (BER), where it is activated by and binds to DNA breaks and catalyzes the poly(ADP-ribosyl)ation of several substrates involved in DNA damage repair. Here we demonstrate that PARP1 associates with telomere repeat binding factor 2 (TRF2) and is capable of poly(ADP-ribosyl)ation of TRF2, which affects binding of TRF2 to telomeric DNA. Immunostaining of interphase cells or metaphase spreads shows that PARP1 is detected sporadically at normal telomeres, but it appears preferentially at eroded telomeres caused by telomerase deficiency or damaged telomeres induced by DNA-damaging reagents. Although PARP1...
71.
Sp2 Localizes to Subnuclear Foci Associated with the Nuclear MatrixV? - Moorefield, K. Scott; Yin, Haifeng; Nichols, Teresa D.; Cathcart, Christopher; Simmons, Steven O.; Horowitz, Jonathan M.
We have reported that extracts prepared from many human and mouse cell lines show little or no Sp2 DNA-binding activity and that Sp2 has little or no capacity to stimulate transcription of promoters that are activated by Sp1, Sp3, and Sp4. Using an array of chimeric Sp1/Sp2 proteins we showed further that Sp2 DNA-binding activity and trans-activation are each negatively regulated in mammalian cells. As part of an ongoing effort to study Sp2 function and regulation we characterized its subcellular localization in comparison with other Sp-family members in fixed and live cells. We report that 1) Sp2 localizes largely within...
72.
Rad22Rad52-dependent Repair of Ribosomal DNA Repeats Cleaved by Slx1-Slx4 Endonuclease - Coulon, Stéphane; Noguchi, Eishi; Noguchi, Chiaki; Du, Li-Lin; Nakamura, Toru M.; Russell, Paul
Slx1 and Slx4 are subunits of a structure-specific DNA endonuclease that is found in Saccharomyces cerevisiae, Schizosaccharomyces pombe, and other eukaryotic species. It is thought to initiate recombination events or process recombination structures that occur during the replication of the tandem repeats of the ribosomal DNA (rDNA) locus. Here, we present evidence that fission yeast Slx1-Slx4 initiates homologous recombination events in the rDNA repeats that are processed by a mechanism that requires Rad22 (Rad52 homologue) but not Rhp51 (Rad51 homologue). Slx1 is required to generate ?50% of the spontaneous Rad22 DNA repair foci that occur in cycling cells. Most of...
73.
Rab1 Defines a Novel Pathway Connecting the Pre-Golgi Intermediate Compartment with the Cell PeripheryV? - Sannerud, Ragna; Marie, Michaël; Nizak, Clément; Dale, Hege Avsnes; Pernet-Gallay, Karin; Perez, Franck; Goud, Bruno; Saraste, Jaakko
The function of the pre-Golgi intermediate compartment (IC) and its relationship with the endoplasmic reticulum (ER) and Golgi remain only partially understood. Here, we report striking segregation of IC domains in polarized PC12 cells that develop neurite-like processes. Differentiation involves expansion of the IC and movement of Rab1-containing tubules to the growth cones of the neurites, whereas p58- and COPI-positive IC elements, like rough ER and Golgi, remain in the cell body. Exclusion of Rab1 effectors p115 and GM130 from the neurites further indicated that the centrifugal, Rab1-mediated pathway has functions that are not directly related to ER-to-Golgi trafficking. Disassembly...
74.
Distinct Roles for the Essential MYST Family HAT Esa1p in Transcriptional SilencingD? - Clarke, Astrid S.; Samal, Eva; Pillus, Lorraine
Among acetyltransferases, the MYST family enzyme Esa1p is distinguished for its essential function and contribution to transcriptional activation and DNA double-stranded break repair. Here we report that Esa1p also plays a key role in silencing RNA polymerase II (Pol II)-transcribed genes at telomeres and within the ribosomal DNA (rDNA) of the nucleolus. These effects are mediated through Esa1p's HAT activity and correlate with changes within the nucleolus. Esa1p is enriched within the rDNA, as is the NAD-dependent protein deacetylase Sir2p, and the acetylation levels of key Esa1p histone targets are reduced in the rDNA in esa1 mutants. Although mutants of...
75.
H-Ras, R-Ras, and TC21 Differentially Regulate Ureteric Bud Cell Branching Morphogenesis - Pozzi, Ambra; Coffa, Sergio; Bulus, Nada; Zhu, Wenqin; Chen, Dong; Chen, Xiwu; Mernaugh, Glenda; Su, Yan; Cai, Songmin; Singh, Amar; Brissova, Marcela; Zent, Roy
The collecting system of the kidney, derived from the ureteric bud (UB), undergoes repetitive bifid branching events during early development followed by a phase of tubular growth and elongation. Although members of the Ras GTPase family control cell growth, differentiation, proliferation, and migration, their role in development of the collecting system of the kidney is unexplored. In this study, we demonstrate that members of the R-Ras family of proteins, R-Ras and TC21, are expressed in the murine collecting system at E13.5, whereas H-Ras is only detected at day E17.5. Using murine UB cells expressing activated H-Ras, R-Ras, and TC21, we...
76.
GSK-3 Is Activated by the Tyrosine Kinase Pyk2 during LPA1-mediated Neurite Retraction - Sayas, C. Laura; Ariaens, Aafke; Ponsioen, Bas; Moolenaar, Wouter H.
Glycogen synthase kinase-3 (GSK-3) is a multifunctional serine/threonine kinase that is usually inactivated by serine phosphorylation in response to extracellular cues. However, GSK-3 can also be activated by tyrosine phosphorylation, but little is known about the upstream signaling events and tyrosine kinase(s) involved. Here we describe a G protein signaling pathway leading to GSK-3 activation during lysophosphatidic acid (LPA)-induced neurite retraction. Using neuronal cells expressing the LPA1 receptor, we show that LPA1 mediates tyrosine phosphorylation and activation of GSK-3 with subsequent phosphorylation of the microtubule-associated protein tau via the Gi-linked PIP2 hydrolysis-Ca2+ mobilization pathway. LPA concomitantly activates the Ca2+-dependent tyrosine...
77.
DNA Damage Signaling and p53-dependent Senescence after Prolonged ?-Interferon StimulationD? - Moiseeva, Olga; Mallette, Frédérick A.; Mukhopadhyay, Utpal K.; Moores, Adrian; Ferbeyre, Gerardo
Interferons are cytokines with potent antiviral and antiproliferative activities. We report that although a transient exposure to ?-interferon induces a reversible cell cycle arrest, a sustained treatment triggers a p53-dependent senescence program. ?-Interferon switched on p53 in two steps. First, it induced the acetylation of p53 at lysine 320 and its dephosphorylation at serine 392 but not p53 activity. Later on, it triggered a DNA signaling pathway, the phosphorylation of p53 at serine 15 and its transcriptional activity. In agreement, ?-interferontreated cells accumulated ?-H2AX foci and phosphorylated forms of ATM and CHK2. The DNA damage signaling pathway was activated by...
78.
Yeast AMID Homologue Ndi1p Displays Respiration-restricted Apoptotic Activity and Is Involved in Chronological Aging - Li, Wei; Sun, Libo; Liang, Qiuli; Wang, Juan; Mo, Weike; Zhou, Bing
Apoptosis-inducing factor (AIF) and AIF-homologous mitochondrion-associated inducer of death (AMID) are both mitochondrial flavoproteins that trigger caspase-independent apoptosis. Phylogenetic analysis suggests that these two proteins evolutionarily diverge back from their common prokaryote ancestor. Compared with AIF, the proapoptotic nature of AMID and its mode of action are much less clarified. Here, we show that overexpression of yeast AMID homologue internal NADH dehydrogenase (NDI1), but not external NADH dehydrogenase (NDE1), can cause apoptosis-like cell death, and this effect can be repressed by increased respiration on glucose-limited media. This result indicates that the regulatory network of energy metabolism, in particular the cross-talk...
79.
CD99 Acts as an Oncosuppressor in Osteosarcoma - Manara, Maria Cristina; Bernard, Ghislaine; Lollini, Pier-Luigi; Nanni, Patrizia; Zuntini, Monia; Landuzzi, Lorena; Benini, Stefania; Lattanzi, Giovanna; Sciandra, Marika; Serra, Massimo; Colombo, Mario Paolo; Bernard, Alain; Picci, Piero; Scotlandi, Katia
CD99 was recently reported to be under control of the osteoblast-specific transcription factor Cbfa1 (RUNX2) in osteoblasts, suggesting a role in the phato-physiology of these cells. No extensive information is available on the role(s) of this molecule in malignant phenotype, and osteosarcoma, in particular, has never been studied. We report that in 11 different cell lines and 17 clinical samples CD99 expression is either undetectable or very low. Being expressed in the normal counterpart, we tested the hypothesis that CD99 down-regulation may have a role in osteosarcoma development and progression. CD99-forced expression in two osteosarcoma cell lines significantly reduced resistance...
80.
Cooperation between Snail and LEF-1 Transcription Factors Is Essential for TGF-?1-induced Epithelial-Mesenchymal TransitionD? - Medici, Damian; Hay, Elizabeth D.; Goodenough, Daniel A.
Transforming growth factor beta 1 (TGF-?1) has been shown to induce epithelial-mesenchymal transition (EMT) during various stages of embryogenesis and progressive disease. This alteration in cellular morphology is typically characterized by changes in cell polarity and loss of adhesion proteins such as E-cadherin. Here we demonstrate that EMT is associated with loss of claudin-1, claudin-2, occludin, and E-cadherin expression within 72 h of exposure to TGF-?1 in MDCKII cells. It has been suggested that this expression loss occurs through TGF-?1 in a Smad-independent mechanism, involving MEK and PI3K pathways, which have previously been shown to induce expression of the Snail...
61.
