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J M Peters

Publications and source records attributed to J M Peters.

At least 127 records · Page 7Linked to original sources
PubMed1996

Anaphase initiation in Saccharomyces cerevisiae is controlled by the APC-dependent degradation of the anaphase inhibitor Pds1p.

Anaphase initiation has been postulated to be controlled through the ubiquitin-dependent proteolysis of an unknown inhibitor. This process involves the anaphase promoting complex (APC), a specific ubiquitin ligase that has been shown to be involved in mitotic cyclin degradation. Previous studies demonstrated that in Saccharomyces cerevisiae, Pds1 protein is an anaphase inhibitor and suggested that it may be an APC target. Here we show that in yeast cells and in mitotic Xenopus extracts Pds1p is degraded in an APC-dependent manner. In addition, Pds1p is directly ubiquitinated by the Xenopus APC. In budding yeast Pds1p is degraded at the time of anaphase initiation and nondegradable derivatives of Pds1p inhibit the onset of anaphase. We conclude that Pds1p is an anaphase inhibitor whose APC-dependent degradation is required for the initiation of anaphase.

Anaphase↗
PubMed1996

How proteolysis drives the cell cycle.

Oscillations in the activity of cyclin-dependent kinases (CDKs) promote progression through the eukaryotic cell cycle. This review examines how proteolysis regulates CDK activity-by degrading CDK activators or inhibitors-and also how proteolysis may directly trigger the transition from metaphase to anaphase. Proteolysis during the cell cycle is mediated by two distinct ubiquitin-conjugation pathways. One pathway, requiring CDC34, initiates DNA replication by degrading a CDK inhibitor. The second pathway, involving a large protein complex called the anaphase-promoting complex or cyclosome, initiates chromosome segregation and exit from mitosis by degrading anaphase inhibitors and mitotic cyclins. Proteolysis therefore drives cell cycle progression not only by regulating CDK activity, but by directly influencing chromosome and spindle dynamics.

Anaphase↗
PubMed1996

Identification of BIME as a subunit of the anaphase-promoting complex.

The initiation of anaphase and exit from mitosis require the activation of a proteolytic system that ubiquitinates and degrades cyclin B. The regulated component of this system is a large ubiquitin ligase complex, termed the anaphase-promoting complex (APC) or cyclosome. Purified Xenopus laevis APC was found to be composed of eight major subunits, at least four of which became phosphorylated in mitosis. In addition to CDC27, CDC16, and CDC23, APC contained a homolog of Aspergillus nidulans BIME, a protein essential for anaphase. Because mutation of bimE can bypass the interphase arrest induced by either nimA mutation or unreplicated DNA, it appears that ubiquitination catalyzed by APC may also negatively regulate entry into mitosis.

Amino Acid Sequence↗
PubMed1996

The PPARalpha-leukotriene B4 pathway to inflammation control.

Inflammation is a local immune response to 'foreign' molecules, infection and injury. Leukotriene B4, a potent chemotactic agent that initiates, coordinates, sustains and amplifies the inflammatory response, is shown to be an activating ligand for the transcription factor PPARalpha. Because PPARalpha regulates the oxidative degradation of fatty acids and their derivatives, like this lipid mediator, a feedback mechanism is proposed that controls the duration of an inflammatory response and the clearance of leukotriene B4 in the liver. Thus PPARalpha offers a new route to the development of anti- or pro-inflammatory reagents.

Adaptation, Physiological↗
PubMed1996

Identification of a novel ubiquitin-conjugating enzyme involved in mitotic cyclin degradation.

BACKGROUND: The destruction of cyclin B is required for exit from mitosis, and is mediated by the ubiquitin pathway. Recently, a 20S complex, termed the anaphase-promoting complex (APC) or the cyclosome, has been genetically and biochemically identified as the cyclin-specific ubiquitin ligase (E3). In addition, a ubiquitin-conjugating enzyme (E2), UBC4, was shown to be involved in cyclin ubiquitination in Xenopus egg extracts. Another E2 activity, designated UBCx, can independently support cyclin ubiquitination in Xenopus. A similar activity (E2-C) has also been observed in clams. However, the molecular identity of Xenopus UBCx or clam E2-C has not been established. RESULTS: We have purified and cloned Xenopus UBCx. Sequence comparisons with known E2s reveal that UBCx is a novel ubiquitin-conjugating enzyme. Purified recombinant UBCx is sufficient to complement purified APC and E1 in destruction box-dependent cyclin ubiquitination. UBCx and UBC4 are active in a similar concentration range and with similar kinetics. At saturating enzyme concentrations, UBCx converts twice as much substrate into ubiquitin conjugates, but generates conjugates of lower molecular mass than UBC4. CONCLUSIONS: UBCx is a novel ubiquitin-conjugating enzyme involved in cyclin ubiquitination in Xenopus. Like UBC4, ubiquitination catalyzed by UBCx is dependent on both the destruction box and the APC, suggesting that these E2s function through a similar mechanism. However, as the patterns of conjugates generated by these E2s are distinct, these enzymes may play different roles in promoting cyclin proteolysis in mitosis.

Amino Acid Sequence↗
PubMed1996

Standardization of multiple spirometers at widely separated times and places.

We designed a system for a multiyear longitudinal study of lung function in 12 widely separated communities, intending to minimize variation in instrument-related data. We used multiple rolling-seal spirometer/personal computer systems. Calibrations were checked before, during, and after each day's field testing, using multiple calibration syringes with electronic readouts. The syringes were rotated to obtain data for each syringe-spirometer combination. Before and after each annual field testing season, a laboratory reference spirometer system was calibrated against a water-displacement device and an electronic frequency counter, and then compared against each field spirometer and syringe. Field equipment consistently met American Thoracic Society (ATS) specifications. Variance among spirometers exceeded variance among syringes. A spirometer occasionally changed its volume readout by approximately 1 to 2 %. More rarely, a syringe changed its delivered volume by approximately 1%. Syringes' electronic readouts tracked changes in delivered volume. Syringe readouts were the most stable component of the system, and were more reproducible than the laboratory water-displacement calibration. We conclude that variation in spirometers may limit the reliability of epidemiologic findings, even when these spirometers meet ATS specifications. Frequent calibration checks traceable to an independent standard, and adjustment of individual test results, can reduce measurement error.

Calibration↗
PubMed1996

Radiosensitive target in the mouse embryo chimera assay: implications that the target involves autocrine growth factor function.

Mouse preimplantation embryos express at least two functional cell surface growth factor receptors that are radiosensitive in other cell types, the epidermal growth factor receptor (EGF receptor) and the insulin-like growth factor I receptor (IGF-I receptor). These embryos also express ligands that bind to and activate these receptors, including transforming growth factor alpha (TGF-alpha) and insulin-like growth factor II (IGF-II), which bind to the EGF receptor and IGF-I receptor, respectively. Embryo-expressed IGF-II and TGF-alpha increase embryo cell number--a measure of proliferation rate--and stimulate blastocoele formation--a measure of cell differentiation--allowing the embryo to self-modulate cell proliferation and morphogenesis into a blastocyst (Paria and Dey, Proc. Natl. Acad. Sci. USA 87, 4756-4760, 1990; Dardik and Schultz, Development 113, 919-930, 1991; Rappolee et al., Genes Dev. 6, 939-952, 1992). In this work, we tested the hypothesis that IGF-I receptor and/or EGF receptor function may be impaired to produce the radiation-induced competitive cell proliferation disadvantage that is expressed by irradiated embryos that are aggregated with nonirradiated embryos in chimeras. Cleavage-stage embryos were irradiated with 137Cs gamma rays (0.5 or 1.0 Gy) and paired with nonirradiated same-stage embryos to form groups of chimeras that were cultured in control medium or medium containing IGF-II, insulin, EGF or TGF-alpha. The cell proliferation disadvantage expressed by the irradiated embryos within chimeras was completely eliminated by IGF-II or insulin. In contrast to the rescue action of IGF-II or insulin in chimeras, neither EGF nor TGF-alpha could prevent the cell proliferation disadvantage exhibited by irradiated embryos paired with nonirradiated embryos in chimeras. For irradiated conventionally cultured zona-enclosed embryos, IGF-II and TGF-alpha did not increase mean embryo cell number significantly, although both IGF-II and TGF-alpha did increase blastocoele formation significantly. Collectively, these results support the following conclusions: (1) Ligands for the IGF-I receptor can rescue irradiated embryos from competitive cell proliferation disadvantage in chimeras, while ligands for the EGF receptor cannot; (2) IGF-I receptor function and EGF receptor function are affected differently by ionizing radiation with respect to competitive cell proliferation and are affected similarly by ionizing radiation with respect to blastocoele formation; (3) EGF receptor-dependent stimulation of competitive cell proliferation and cell differentiation are affected differently by ionizing radiation in preimplantation embryos.

Animals↗
PubMed1996

Peroxisome proliferator-activated receptor alpha required for gene induction by dehydroepiandrosterone-3 beta-sulfate.

Peroxisome proliferator-activated receptor alpha (PPAR alpha) mediates the effects of foreign chemical peroxisome proliferators on liver and kidney, including the induction of peroxisomal, mitochondrial, and microsomal enzymes involved in beta-oxidation of fatty acids. However, the role of this receptor in the peroxisome proliferative effects of the endogenous steroid dehydroepiandrosterone (DHEA) is not known. DHEA-3 beta-sulfate fd(DHEA-S) is shown to induce a liver peroxisome proliferative response in rats in vivo at a dose at which DHEA is much less active, which is consistent with cultured hepatocyte studies indicating a requirement for sulfation for the activation of DHEA. Transient transfection experiments demonstrated that in contrast to the prototypic foreign chemical peroxisome proliferator pirinixic acid, DHEA-S and its 17 beta-reduced metabolite, 5-androstene-3 beta, 17 beta-diol-3 beta-sulfate, are inactive in mediating trans-activation by PPAR alpha in COS-1 cells. Two other mammalian PPAR isoforms, gamma and delta/Nucl, were also inactive with respect to DHEA-S trans-activation. To test whether PPAR alpha mediates peroxisomal gene induction by DHEA-S in intact animals, we administered DHEA-S or clofibrate to mice lacking a functional PPAR alpha gene. Both peroxisome proliferators markedly increased hepatic expression of two microsomal cytochrome P450 4A proteins as well as six mRNAs known to be associated with the peroxisomal proliferative response in wild-type mice. In contrast, neither DHEA-S nor clofibrate induced these hepatic proteins and mRNAs in PPAR alpha-deficient mice. Clofibrate-induced expression of kidney CYP4A mRNAs was also blocked in the PPAR alpha gene knockout mice. Thus, despite its unresponsiveness to steroidal peroxisome proliferators in transfection assays, PPAR alpha is obligatory for DHEA-S-stimulated hepatic peroxisomal gene induction. DHEA-S, or one of its metabolites, may thus serve as an important endogenous regulator of liver peroxisomal enzyme expression via a PPAR alpha-mediated pathway.

Acetophenones↗
PubMed1995

The ATPase activity of purified CDC48p from Saccharomyces cerevisiae shows complex dependence on ATP-, ADP-, and NADH-concentrations and is completely inhibited by NEM.

The cell cycle protein CDC48p from Saccharomyces cerevisiae is a member of a protein superfamily (AAA superfamily) characterized by a common region of approximately 200 amino-acid residues including an ATP binding consensus. CDC48p purified to homogeneity showed considerable ATPase activity which could be completely abolished by preincubation with NEM in the absence of ATP. ATP protects the protein from NEM and stabilizes the otherwise labile enzyme. The ATPase activity is reversibly inhibited by NADH and shows cooperativity with its substrate ATP. The application of the in vitro ATPase activity to the identification of physiologically interacting molecules is discussed. By electron microscopy, the enzyme was shown to consist of hexameric ring structures similar to its vertebrate homologue.

Adenosine Diphosphate↗
PubMed1995

The formation of Golgi stacks from vesiculated Golgi membranes requires two distinct fusion events.

We have reconstituted the fusion and assembly of vesiculated Golgi membranes (VGMs) into functionally active stacks of cisternae. A kinetic analysis of this assembly process revealed that highly dispersed VGMs of 60-90 nm diameter first fuse to form larger vesicles of 200-300 nm diameter that are clustered together. These vesicles then fuse to form tubular elements and short cisternae, which finally assemble into stacks of cisternae. We now provide evidence that the sequential stack formation from VGMs reflects two distinct fusion processes: the first event is N-ethyl-maleimide (NEM)-sensitive factor (NSF) dependent, and the second fusion event requires an NSF-like NEM-sensitive ATPase called p97. Interestingly, while the earliest steps in stack formation share some similarities with events catalyzing fusion of transport vesicles to its target membrane, neither GTP gamma S nor Rab-GDI, inhibitors of vesicular protein traffic, inhibit stack formation.

Carrier Proteins↗
PubMed1995

An NSF-like ATPase, p97, and NSF mediate cisternal regrowth from mitotic Golgi fragments.

Golgi cisternae regrew in a cell-free system from mitotic Golgi fragments incubated with buffer alone. Pretreatment with NEM or salt washing inhibited regrowth, but this could be restored either by p97, an NSF-like ATPase, or by NSF together with SNAPs and p115, a vesicle docking protein. The morphology of cisternae regrown with p97 and NSF-SNAPs-p115 differed, suggesting that they play distinct roles in rebuilding Golgi cisternae after mitosis.

Adenosine Triphosphatases↗
PubMed1995

Influence of antioxidants on cadmium toxicity of mouse preimplantation embryos in vitro.

To test the hypothesis that the developmental toxicity of cadmium (Cd) is due in part to oxidative damage, embryos were cultured in medium containing 0.0, 1.0, 3.0, or 6.0 microM Cd with or without various antioxidants for 72 h. Ascorbate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and glutathione (GSH) were all effective at ameliorating 1.0 microM Cd-induced embryotoxicity. For embryos cultured in medium containing either 3.0 or 6.0 microM Cd, GSH was effective at ameliorating Cd toxicity while the other antioxidants tested were ineffective. Pretreating embryos with antioxidants for 24 h prior to exposing them to Cd and antioxidants did not significantly alter the previously observed improvement with the exception that pretreatment with GSH virtually eliminated Cd-induced embryotoxicity between 1.0 and 6.0 microM Cd. A 4-h exposure to GSH prior to culture in Cd markedly improved embryo development suggesting that GSH taken up during pretreatment can provide protection against Cd-induced embryotoxicity. This work supports the hypothesis that the developmental toxicity of Cd is in part due to oxidative damage that can be modulated by select antioxidants.

Analysis of Variance↗
PubMed1995

Maternity assignment and queen replacement in a social wasp.

Assigning offspring to parents is important for understanding the evolution of reproductive conflicts and cooperation, particularly in the model systems represented by social insects. Molecular genetic markers are often used to exclude, and occasionally used to assign, candidate parents. However, their use in social insects has been unsatisfactory so far because candidate mothers are often highly related and candidate fathers are unknown. Here, we show that microsatellite loci can be scored from each mother's stored sperm permitting effective maternity assignment. The theoretical power of this method is huge, and we demonstrate its practical utilization in this large-scale study of the wasp, Polistes annularis. All 219 genotyped daughters were either assigned to a unique mother or shown to be the progeny of an uncollected dead mother. The data reveal an unexpectedly high number of changes in reproductive dominance. Maternity assignments using this method should help solve many difficult questions in social evolution.

Alleles↗
PubMed1995

A 20S complex containing CDC27 and CDC16 catalyzes the mitosis-specific conjugation of ubiquitin to cyclin B.

Cyclin B is degraded at the onset of anaphase by a ubiquitin-dependent proteolytic system. We have fractionated mitotic Xenopus egg extracts to identify components required for this process. We find that UBC4 and at least one other ubiquitin-conjugating enzyme can support cyclin B ubiquitination. The mitotic specificity of cyclin ubiquitination is determined by a 20S complex that contains homologs of budding yeast CDC16 and CDC27. Because these proteins are required for anaphase in yeast and mammalian cells, we refer to this complex as the anaphase-promoting complex (APC). CDC27 antibodies deplete APC activity, while immunopurified CDC27 complexes are sufficient to complement either interphase extracts or a mixture of recombinant UBC4 and the ubiquitin-activating enzyme E1. These results suggest that APC functions as a regulated ubiquitin-protein ligase that targets cyclin B for destruction in mitosis.

Anaphase↗
PubMed1995

Hypothesis: the risk of childhood leukemia is related to combinations of power-frequency and static magnetic fields.

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-frequency (ELF) magnetic fields. Laboratory data from calcium efflux and diatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of the static field magnitude with a bandwidth of 9.1 microT that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and childhood leukemia using data from a case-control study in Los Angeles County. ELF and static magnetic fields were measured in the bedrooms of 124 cases determined from a tumor registry and 99 controls drawn from friends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicted bands of biological activity centered at 38.0 microT and 50.6 microT. Although no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of leukemia risk with measured ELF fields was found for subjects within these static field bands (P for trend = 0.041). The odds ratio (OR) was 3.3 [95% confidence interval (CI) = 0.4-30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 microT (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 microT). When the 60 Hz magnetic fields were assessed according to the Wertheimer-Leeper code for wiring configurations, leukemia risks were again greater with the hypothesized exposure conditions (OR = 9.2 for very high current configurations within the static field bands; 95% CI = 1.3-64.6). Although the risk estimates are based on limited magnetic field measurements for a small number of subjects, these findings suggest that the risk of childhood leukemia may be related to the combined effects of the static and ELF magnetic fields. Further tests of the hypothesis are proposed.

Calcium↗
PubMed1995

Periconceptional zinc deficiency affects uterine 3H-estradiol binding in mice.

To better define the mechanisms by which zinc (Zn) deficiency influences periconceptional development, we examined the effects of this developmental insult on uterine estrogen metabolism. CD-1 mice were assigned to 1 of 3 groups (Low Zn, LZ; Control, C; or Replete, R) and fed either a low Zn (< or = 0.3 microgram Zn/g) or control diet (47 micrograms Zn/g) 5 days prior to gestation day (GD) 0 and continuing up to GD 4 during early pregnancy. Mice in the R group were fed the low Zn diet until GD 1 after which they were fed the control diet. Uterine 3H-estradiol binding in vivo was measured on GD 2, GD 3, and GD 4. Binding was similar among groups on GD 2 and GD 3, but was lower on GD 4 in LZ mice than in C and R mice (61% of control value). On GD 4, uterine 3H-estradiol binding in vitro was measured and was lower in LZ mice than in C and R mice (63-74% of control values); the reduction in binding was due to lower receptor number. Thus, Zn deficiency can result in a reduction in uterine estradiol receptors and estradiol binding.

Animals↗