The Stomatin-Like Protein SLP-1 and Cdk2 Interact with the F-Box Protein Fbw7-γ

Control of cellular proliferation is critical to cell viability. The F-box protein Fbw7 (hAgo/hCdc4/FBXW7) functions as a specificity factor for the Skp1-Cul1-F-box protein (SCF) ubiquitin ligase complex and targets several proteins required for cellular proliferation for ubiquitin-mediated destruction. Fbw7 exists as three splice variants but the mechanistic role of each is not entirely clear. We examined the regulation of the Fbw7-γ isoform, which has been implicated in the degradation of c-Myc. We show here that Fbw7-γ is an unstable protein and that its turnover is proteasome-dependent in transformed cells. Using a two-hybrid screen, we identified a novel interaction partner, SLP-1, which binds the N-terminal domain of Fbw7-γ. Overexpression of SLP-1 inhibits the degradation of Fbw7-γ, suggesting that this interaction can happen in vivo. When Fbw7-γ is stabilized by overexpression of SLP-1, c-Myc protein abundance decreases, suggesting that the SCF^Fbw7-γ complex maintains activity. We demonstrate that Cdk2 also binds the N-terminal domain of Fbw7-γ as well as SLP-1. Interestingly, co-expression of Cdk2 and SLP-1 does not inhibit Fbw7-γ degradation, suggesting that Cdk2 and SLP-1 may have opposing functions.     

Bacterial metabolism of chlorinated dehydroabietic acids occurring in pulp and paper mill effluents

Chlorinated dehydroabietic acids are formed during the chlorine bleaching of wood pulp and are very toxic to fish. Thus, destruction of these compounds is an important function of biological treatment systems for pulp and paper mill effluents. In this study, 12 strains of diverse, aerobic resin acid-degrading bacteria were screened for the ability to grow on chlorinated dehydroabietic acids as sole organic substrates. All seven strains of the class Proteobacteria able to use dehydroabietic acid were also able to use a mixture of 12- and 14-chlorodehydroabietic acid (Cl-DhA). None of the strains used 12,14-dichlorodehydroabietic acid. Sphingomonas sp. strain DhA-33 grew best on Cl-DhA and simultaneously removed both Cl-DhA isomers. Ralstonia sp. strain BKME-6 was typical of most of the strains tested, growing more slowly on Cl-DhA and leaving higher residual concentrations of Cl-DhA than DhA-33 did. Strains DhA-33 and BKME-6 mineralized (converted to CO(inf2) plus biomass) 32 and 43%, respectively, of carbon in Cl-DhA consumed. Strain DhA-33 produced a metabolite from Cl-DhA, tentatively identified as 3-oxo-14-chlorodehydroabietin, and both strains produced dissolved organic carbon which may include unidentified metabolites. Cl-DhA removal was inducible in both DhA-33 and BKME-6, and induced DhA-33 cells also removed 12,14-dichlorodehydroabietic acid. Based on activities of strains DhA-33 and BKME-6, chlorinated DhAs, and potentially toxic metabolite(s) of these compounds, are relatively persistent in biological treatment systems and in the environment.     

THE OPTIMUM PH OF FOUR STRAINS OF ACIDOPHILIC SNOW ALGAE IN THE GENUS CHLOROMONAS (CHLOROPHYTA) AND POSSIBLE EFFECTS OF ACID PRECIPITATION1

Four axenic strains of snow algae were examined for optimum pH under laboratory conditions using M-1 growth medium. Growth was measured using cell counts, cell measurements and absorbance readings at 440 nm. Strains C204 and C479A of Chloromonas sp. from the Adirondack Mountains, New York, grew optimally at pH 4.0 to 5.0. Strains C381F and C381G, Chloromonas polyptera (Fritsch) Hoh., Mull. & Roem. from the White Mountains, Arizona, grew optimally at pH 4.5 to 5.0. Growth was significantly higher at pH 4.0 in the northeastern species (Chloromonas sp.), but no significant difference was observed in final growth at pH 4.5, 5.0 and 5.5 between species. It is postulated that the more acidic precipitation in the northeastern United States may be selecting for strains of snow algae with greater tolerance to acidity than in strains from the southwestern United States or that the different pH optima reported are simply species differences. New York strain C204 was also grown in heavily buffered AM medium where it had an optimum pH of 5.0, but cells became irregularly shaped and tended to clump at pH 6.0 to 7.0. Growth of C204 in AM medium was significantly lower than in M-1 medium for snow algae. These findings justify the use of M-1 medium for this type of experimentation.     

Macroangiopathy in adults and children with diabetes: risk factors (part 2).

Autoimmune or type 1 diabetes mellitus (T1DM), accounts for 90-95% of all cases of diabetes, while type 2 diabetes mellitus (T2DM), characterized by impaired insulin sensitivity and production, accounts for the other 5-10%. Atherosclerotic process starts during childhood and recognize several mechanisms that are activated in response to NOXIUS STIMULI and participate in a complex state which is accepted to be a chronic inflammatory state. T1DM patients, especially those with a non-optimal metabolic control, have a higher risk of developing all macrovascular complications such as myocardial infarction, stroke and silent ischemia. Macrovascular disease is mainly associated with hyperglycemia, dyslipidemia, obesity, hypertension, hypercoagulable state, cigarette smoking, lack of exercise, endothelial dysfunction, hyperhomocysteinemia and vascular wall abnormalities. In this paper we review the importance of traditional and non-traditional risk factors for macrovascular complications in children with T1DM and discuss their role in the pathogenesis of the excess cardiovascular mortality in these patients.     

Adventitious root initiation in hypocotyl and epicotyl cuttings of eastern white pine (Pinus strobus) seedlings

The present paper reports results of experiments to develop a system for studying adventitious root initiation in cuttings derived from seedlings. Hypocotyl cuttings of 2-week-old eastern white pine (Pinus strobus L.) seedlings were treated for 5 min with 0, 100, 200, 300, 400, 500 or 600 mg l^?1 (0, 0.54, 1.07, 1.61, 2.15, 2.69 or 3.22 mM) 1-naphthaleneacetic acid (NAA) to determine the effect on root initiation. The number of root primordia per cutting was correlated with NAA concentration and the square of NAA concentration. Thus, the number increased from less than one per cutting in the 0 NAA treatment to approximately 40 per cutting at 300 mg l-1 NAA, above which no substantial further increase was observed. The larger number of root primordia formed in response to increasing concentrations of NAA was due to the formation of primordia over a larger proportion of the hypocotyls. Histological analysis of the timing of root primordium formation in hypocotyl cuttings revealed three discernible stages. Progression through these stages was relatively synchronous among NAA-treated hypocotyl cuttings and within a given cutting, but variation was observed in the portion of different cuttings undergoing root formation. Control-treated hypocotyl cuttings formed root primordia at lower frequencies and more slowly than NAA-treated cuttings, with fewer primordia per cutting. Epicotyl cuttings from 11-week-old seedlings also formed adventitious roots, but more slowly than hypocotyl cuttings. NAA treatment of epicotyl cuttings caused more rapid root initiation and also affected the origin of adventitious roots in comparison with nontreated cuttings. NAA-treated epicotyl cuttings formed roots in a manner analogous to that of the hypocotyl cuttings, directly from preformed vascular tissue, while control-treated epicotyl cuttings first formed a wound or callus tissue and subsequently differentiated root primordia within that tissue. This system of inducing adventitious roots in pine stem cuttings lends itself to studying the molecular and biochemical steps that occur during root initiation and development.     

Short Inverted-Repeat Transposable Elements in Teleost Fish and Implications for a Mechanism of Their Amplification

Angel is the first miniature inverted-repeat transposable element (MITE) isolated from fish. Angel elements are imperfect palindromes with the potential to form stem-loop structures in vitro. Despite sequence divergence of elements of up to 55% within and between species, their inverted repeat structures have been maintained, implying functional importance. We estimate that there are about 10³–10⁴ Angels scattered throughout the zebrafish genome, evidence that this family of transposable elements has been significantly amplified over the course of evolution. Angel elements and Xenopus MITEs carry common sequence motifs at their termini, indicating common origin and/or related mechanisms of transposition. We present a model in which MITEs take advantage of the basic cellular mechanism of DNA replication for their amplification, which is dependent on the characteristic inverted repeat structures of these elements. We propose that MITEs are genomic parasites that transpose via a DNA intermediate, which forms by a folding-back of a single strand of DNA, that borrow all of the necessary factors for their amplification from products encoded in the genomes in which they reside. DNA polymorphisms in different lines of zebrafish were detected by PCR using Angel-specific primers, indicating that such elements, combined with other transposons in vertebrate genomes, will be useful molecular tools for genome mapping and genetic analyses of mutations. Received: 7 April 1998 / Accepted: 7 April 1998     

Differences in field‐scale N2O flux linked to crop residue removal under two tillage systems in cold climates

Residue removal for biofuel production may have unintended consequences for N₂O emissions from soils, and it is not clear how N₂O emissions are influenced by crop residue removal from different tillage systems. Thus, we measured field‐scale N₂O flux over 5 years (2005–2007, 2010–2011) from an annual crop rotation to evaluate how N₂O emissions are influenced by no‐till (NT) compared to conventional tillage (CV), and how crop residue removal (R?) rather than crop residue return to soil (R+) affects emissions from these two tillage systems. Data from all 5 years indicated no differences in N₂O flux between tillage practices at the onset of the growing season, but CT had 1.4–6.3 times higher N₂O flux than NT overwinter. Nitrous oxide emissions were higher due to R? compared to R+, but the effect was more marked under CT than NT and overwinter than during spring. Our results thus challenge the assumption based on IPCC methodology that crop residue removal will result in reduced N₂O emissions. The potential for higher N₂O emission with residue removal implies that the benefit of utilizing biomass as biofuels to mitigate greenhouse gas emission may be overestimated. Interestingly, prior to an overwinter thaw event, dissolved organic C (DOC) was negatively correlated to peak N₂O flux (r = ?0.93). This suggests that lower N₂O emissions with R+ vs. R? may reflect more complete stepwise denitrification to N₂ during winter and possibly relate to the heterotrophic microbial capacity for processing crop residue into more soluble C compounds and a shift in the preferential C source utilized by the microbial community overwinter.