Peptide Interactions Stabilize and Restructure Human Papillomavirus Type 16 E6 To Interact with p53

Human papillomavirus type 16 (HPV-16) E6 (16E6) binds the E3 ubiquitin ligase E6AP and p53, thereby targeting degradation of p53 (M. Scheffner, B. A. Werness, J. M. Huibregtse, A. J. Levine, and P. M. Howley, Cell 63:1129–1136, 1990). Here we show that minimal 16E6-binding LXXLL peptides reshape 16E6 to confer p53 interaction and stabilize 16E6 in vivo but that degradation of p53 by 16E6 requires E6AP expression. These experiments establish a general mechanism for how papillomavirus E6 binding to LXXLL peptides reshapes E6 to then act as an adapter molecule.     

Catecholamine and insulin control of lipolysis in subcutaneous adipose tissue during long-term diet-induced weight loss in obese women

The aim of this study was to investigate the evolution of the adrenergic and insulin-mediated regulation of lipolysis during different phases of a 6-mo dietary intervention. Eight obese women underwent a 6-mo dietary intervention consisting of a 1-mo very low-calorie diet (VLCD) followed by a 2-mo low-calorie diet (LCD) and 3-mo weight maintenance (WM) diet. At each phase of the dietary intervention, microdialysis of subcutaneous adipose tissue (SCAT) was performed at rest and during a 3-h hyperinsulinemic euglycemic clamp. Responses of dialysate glycerol concentration (DGC) were determined at baseline and during local perfusions with adrenaline or adrenaline and phentolamine before and during the last 30 min of the clamp. Dietary intervention induced a body weight reduction and an improved insulin sensitivity. DGC progressively decreased during the clamp, and this decrease was similar during the different phases of the diet. The adrenaline-induced increase in DGC was higher at VLCD and LCD compared with baseline condition and returned to prediet levels at WM. In the probe with adrenaline and phentolamine, the increase in DGC was higher than that in the adrenaline probe at baseline and WM, but it was not different at VLCD and LCD. The results suggest that the responsiveness of SCAT to adrenaline-stimulated lipolysis increases during the calorie-restricted phases due to a reduction of the α(2)-adrenoceptor-mediated antilipolytic action of adrenaline. At WM, adrenaline-stimulated lipolysis returned to the prediet levels. Furthermore, no direct relationship between insulin sensitivity and the diet-induced changes in the regulation of lipolysis was found.     

Draft genome sequence of the volcano-inhabiting thermoacidophilic methanotroph Methylacidiphilum fumariolicum strain SolV

The draft genome of Methylacidiphilum fumariolicum SolV, a thermoacidophilic methanotroph of the phylum Verrucomicrobia, is presented. Annotation revealed pathways for one-carbon, nitrogen, and hydrogen catabolism and respiration together with central metabolic pathways. The genome encodes three orthologues of particulate methane monooxygenases. Sequencing of this genome will help in the understanding of methane cycling in volcanic environments.     

Variation in personality and behavioural plasticity across four populations of the great tit Parus major

1. Interest in the evolutionary origin and maintenance of individual behavioural variation and behavioural plasticity has increased in recent years. 2. Consistent individual behavioural differences imply limited behavioural plasticity, but the proximate causes and wider consequences of this potential constraint remain poorly understood. To date, few attempts have been made to explore whether individual variation in behavioural plasticity exists, either within or between populations. 3. We assayed 'exploration behaviour' among wild-caught individual great tits Parus major when exposed to a novel environment room in four populations across Europe. We quantified levels of individual variation within and between populations in average behaviour, and in behavioural plasticity with respect to (i) repeated exposure to the room (test sequence), (ii) the time of year in which the assays were conducted and (iii) the interval between successive tests, all of which indicate habituation to novelty and are therefore of functional significance. 4. Consistent individual differences ('I') in behaviour were present in all populations; repeatability (range: 0.34-0.42) did not vary between populations. Exploration behaviour was also plastic, increasing with test sequence - but less so when the interval between subsequent tests was relatively large - and time of year; populations differed in the magnitude of plasticity with respect to time of year and test interval. Finally, the between-individual variance in exploration behaviour increased significantly from first to repeat tests in all populations. Individuals with high initial scores showed greater increases in exploration score than individuals with low initial scores; individual by environment interaction ('I × E') with respect to test sequence did not vary between populations. 5. Our findings imply that individual variation in both average level of behaviour and behavioural plasticity may generally characterize wild great tit populations and may largely be shaped by mechanisms acting within populations. Experimental approaches are now needed to confirm that individual differences in behavioural plasticity (habituation) - not other hidden biological factors - caused the observed patterns of I × E. Establishing the evolutionary causes and consequences of this variation in habituation to novelty constitutes an exciting future challenge.     

Impact of production strategies and animal performance on economic values of dairy sheep traits

The objective of this study was to carry out a sensitivity analysis on the impact of various production strategies and performance levels on the relative economic values (REVs) of traits in dairy sheep. A bio-economic model implemented in the program package ECOWEIGHT was used to simulate the profit function for a semi-extensive production system with the Slovak multi-purpose breed Improved Valachian and to calculate the REV of 14 production and functional traits. The following production strategies were analysed: differing proportions of milk processed to cheese, customary weaning and early weaning of lambs with immediate sale or sale after artificial rearing, seasonal lambing in winter and aseasonal lambing in autumn. Results of the sensitivity analysis are presented in detail for the four economically most important traits: 150 days milk yield, conception rate of ewes, litter size and ewe productive lifetime. Impacts of the differences in the mean value of each of these four traits on REVs of all other traits were also examined. Simulated changes in the production circumstances had a higher impact on the REV for milk yield than on REVs of the other traits investigated. The proportion of milk processed to cheese, weaning management strategy for lambs and level of milk yield were the main factors influencing the REV of milk yield. The REVs for conception rate of ewes were highly sensitive to the current mean level of the trait. The REV of ewe productive lifetime was most sensitive to variation in ewe conception rate, and the REV of litter size was most affected by weaning strategy for lambs. On the basis of the results of sensitivity analyses, it is recommended that economic values of traits for the overall breeding objective for dairy sheep be calculated as the weighted average of the economic values obtained for the most common production strategies of Slovak dairy sheep farms and that economic values be adjusted after substantial changes in performance levels of the traits.     

Transformation by bovine papillomavirus type 1 E6 requires paxillin

Papillomavirus E6 proteins are adapters that change the function of cellular regulatory proteins. The bovine papillomavirus type 1 E6 (BE6) binds to LXXLL peptide sequences termed LD motifs (consensus sequence LDXLLXXL) on the cellular protein paxillin that is a substrate of Src and focal adhesion kinases. Anchorage-independent transformation induced by BE6 required both paxillin and BE6-binding LD motifs on paxillin but was independent of the major tyrosine phosphorylation sites of paxillin. The essential role of paxillin in transformation by BE6 highlights the role of paxillin in the transduction of cellular signals that result in anchorage-independent cell proliferation.     

Overexpression of P-glycoprotein in L1210/VCR cells is associated with changes in several endoplasmic reticulum proteins that may be partially responsible for the lack of thapsigargin sensitivity

L1210/VCR cells, which express an abundant amount of P-glycoprotein (P-gp), were found to be resistant to thapsigargin--an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA). In the current paper, we have studied the possible differences among L1210 and L1210/VCR cells in expression of endoplasmic reticulum proteins involved in the regulation of calcium homeostasis and calcium-dependent processes. Amounts of mRNA encoding both calcium release channels (ryanodine receptor channels--RyR and IP3-receptor channels--IP3R) were found to be at similar levels in sensitive and resistant cells. However, mRNAs encoding IP3R1 or 2 were decreased in resistant cells cultivated in the presence of VCR (1.08 micromol/l), while mRNA encoding RyR remained unchanged. The amount of mRNA for SERCA2 was decreased in resistant cells when compared with sensitive cells. This decrease was more pronounced when resistant cells were cultivated in the presence of vincristine (VCR). Calnexin was found to be less expressed at the protein level in resistant as in sensitive cells. The level of mRNA encoding calnexin was decreased only when resistant cells were cultivated in the presence of VCR. Calnexin was found to be associated with immature P-gp in resistant cells. Thus, differences exist between sensitive and resistant cells in the expression of endoplasmic reticulum proteins involved in the control of intracellular calcium homeostasis or calcium-dependent processes. These changes may be at least partially responsible for the lack of sensitivity of resistant cells to thapsigargin.     

Energy transfer in the peridinin-chlorophyll protein complex reconstituted with mixed chlorophyll sites

We use femtosecond transient absorption spectroscopy to study chlorophyll (Chl)-Chl energy transfer in the peridinin-chlorophyll protein (PCP) reconstituted with mixtures of either chlorophyll b (Chlb) and Chld or Chla and bacteriochlorophyll a (BChla). Analysis of absorption and transient absorption spectra demonstrated that reconstitution with chlorophyll mixtures produces a significant fraction of PCP complexes that contains a different Chl in each domain of the PCP monomer. The data also suggest that binding affinity of Chla is less than that of the other three Chl species. By exciting the Chl species lying at higher energy, we obtained energy transfer times of 40 ± 5 ps (Chlb-Chld) and 59 ± 3 ps (Chla-BChla). The experimental values match those obtained from the Förster equation, 36 and 50 ps, respectively, showing that energy transfer proceeds via the Förster mechanism. Excitation of peridinin in the PCP complex reconstituted with Chla/BChla mixture provided time constants of 2.6 and 0.4 ps for the peridinin-Chla and peridinin-BChla energy transfer, matching those obtained from studies of PCP complexes reconstituted with single chlorophyll species.     

Measures of stratigraphic fit to phylogeny and their sensitivity to tree size, tree shape, and scale

Measures of stratigraphic fit to phylogeny are analyzed to test how they are affected by the shape and size of the phylogenetic trees and by the number of stratigraphic intervals encompassed. Monte Carlo randomizations are used to investigate the sensitivity of three commonly used measures (SCI, GER and MSM*) approximating their distribution of possible values under certain conditions. All are shown to vary in different ways as parameters are varied, although MSM* seems to be the most invariant in the analyzed parameter space. These results suggest that the raw metrics should not be used for comparing the fit of different taxonomic groups or competing phylogenetic trees of the same group that differ in tree size or balance. Tree balance also affects the distributions used in significance tests based on randomization and therefore their results should not be interpreted in terms of the amount of conflict implied by a phylogenetic tree.     

Carotenoid S(1) state in a recombinant light-harvesting complex of Photosystem II.

The carotenoid species lutein, violaxanthin, and zeaxanthin are crucial in the xanthophyll-dependent nonphotochemical quenching occurring in photosynthetic systems of higher plants, since they are involved in dissipation of excess energy and thus protect the photosynthetic machinery from irreversible inhibition. Nonetheless, important properties of the xanthophyll cycle carotenoids, such as the energy of their S(1) electronic states, are difficult to study and were only recently determined in organic solvents [Polívka, T. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 4914. Frank, H. A. (2000) Biochemistry 39, 2831]. In the present study, we have determined the S(1) energies of three carotenoid species, violaxanthin, lutein, and zeaxanthin, in their LHCII (peripheral light-harvesting complex of photosystem II) protein environment by constructing recombinant Lhcb1 (Lhc = light-harvesting complex) proteins containing single carotenoid species. Within experimental error the S(1) energy is the same for all three carotenoids in the monomeric LHCII, 13,900 +/- 300 cm(-1) (720 +/- 15 nm), thus well below the Q(y)() transitions of chlorophylls. In addition, we have found that, although the S(1) lifetimes of violaxanthin, lutein, and zeaxanthin differ substantially in solution, when incorporated into the LHCII protein, their S(1) states have in fact the same lifetime of about 11 ps. Despite the similar spectroscopic properties of the carotenoids bound to the LHCII, we observed a maximal fluorescence quenching when zeaxanthin was present in the LHCII complex. On the basis of these observations, we suggest that, rather than different photochemical properties of individual carotenoid species, changes in the protein conformation induced by binding of carotenoids with distinct molecular structures are involved in the quenching phenomena associated with Lhc proteins.