Methylation of Lysine 9 in Histone H3 Directs Alternative Modes of Highly Dynamic Interaction of Heterochromatin Protein hHP1β with the Nucleosome

Binding of heterochromatin protein 1 (HP1) to the histone H3 lysine 9 trimethylation (H3K9me3) mark is a hallmark of establishment and maintenance of heterochromatin. Although genetic and cell biological aspects have been elucidated, the molecular details of HP1 binding to H3K9me3 nucleosomes are unknown. Using a combination of NMR spectroscopy and biophysical measurements on fully defined recombinant experimental systems, we demonstrate that H3K9me3 works as an on/off switch regulating distinct binding modes of hHP1β to the nucleosome. The methyl-mark determines a highly flexible and very dynamic interaction of the chromodomain of hHP1β with the H3-tail. There are no other constraints of interaction or additional multimerization interfaces. In contrast, in the absence of methylation, the hinge region and the N-terminal tail form weak nucleosome contacts mainly with DNA. In agreement with the high flexibility within the hHP1β-H3K9me3 nucleosome complex, the chromoshadow domain does not provide a direct binding interface. Our results report the first detailed structural analysis of a dynamic protein-nucleosome complex directed by a histone modification and provide a conceptual framework for understanding similar interactions in the context of chromatin.     

Reproductive and socioeconomic determinants of child survival: confounded, interactive, and age-dependent effects.

Studies of infant and child mortality have evolved to distinguish between two sets of explanatory variables-factors related to reproductive or maternal characteristics and socioeconomic factors, generally described as characteristics of the family or household. Almost all multivariate analyses include variables from each of these two sets, but there has been little consideration of the relationship between them. We examine how these two sets of variables jointly affect mortality. We test first for confounded effects by examining socioeconomic effects while excluding and then including reproductive variables in nested multivariate models. Next, we look for age-dependent effects among the explanatory variables and find that reproductive and socioeconomic factors affect mortality at differing ages of children. Finally, we examine interactive effects of the two sets of variables. We conclude that the higher mortality observed among the low status groups is not a result of greater concentration of poor reproductive patterns in those groups. Instead, higher status groups probably have more resources available for combating the negative effects of the same high-risk reproductive patterns.     

Bimolecular fluorescence complementation based on the red fluorescent protein FusionRed

The aim of this work is to construct split variants of the red fluorescent protein FusionRed, each of which consists of two separate polypeptides, nonfluorescent parts of FusionRed, that can form functional fluorescent proteins upon reassociation. At the first stage, various circularly permuted FusionRed variants have been created (in circular permutants the protein polypeptide chain is divided into two parts, which change places so that the C-terminal part is followed by the N-terminal part). Two variants with the highest rate of chromophore maturation (fluorescence development) have been selected out of 23 tested permutation points. These proteins called cpFR76-73 and cpFR189-188 (the first number indicates the last amino acid residue of the N-terminal part; the second number, the first residue of the C-terminal part) are spectrally similar to parental FusionRed but possess lower fluorescence quantum yields. Split variants corresponding to these two circular permutants have been tested in mammalian cells. For reassembly of the fluorescent protein fragments, heterodimerizing leucine zippers have been used. It has been shown that split variant FR189-188 matures at 37°C and possesses fluorescence brightness similar to that of FusionRed. Consequently, FR189-188 is potentially suitable for a wide range of applications, for example, the study of protein–protein interactions or visualization of cell populations, in which two target gene promoters are simultaneously active.     

Morphologie,Anatomie und Systematik carotinoidhaltiger Blätterpilze

Während Carotinoide innerhalb mehrerer natürlicher Verwandtschaftsgruppen der Heterobasidiomyceten charakteristisch und regelmäßig auftreten, ist das Vorkommen dieser Sekundärstoffklasse innerhalb der Homobasidiomyceten auf wenige Arten der corticioiden, clavarioiden, cantharelloiden, agaricoiden und gateroiden Organisationsstufen beschränkt (Tab. 1). Die Anatomie der Fruchtkörper und die Morphologie der Hyphen und Basidien der agaricoiden Vertreter, Phyllotopsis nidulans, Gerronema chrysophyllum, Haasiella venustissima wurden mit verschiedenen lichtmikroskopischen Methoden untersucht. Die gewonnenen Daten wurden mit Mikrophotographien und maßstabsgetreuen Zeichnungen belegt. Die Merkmale von Phyllotopsis nidulans — dickwandige Hyphen in der Fruchtkörpertrama, Medaillonschnallen in der Lamellentrama, sehr schmale Basidien, allantoide Sporen und der Besitz von Zystiden — können bei den anderen Arten nicht gefunden werden. Merulius, Phlebia, Gloeoporus, Auriculariopsis, Dictyoploca u. a. müssen als nah verwandte Gattungen angesehen werden. Die beiden anderen omphalinoid organisierten Blätterpilze, Gerronema chrysophyllum und Haasiella venustissima zeigen trotz Ähnlichkeiten in der Fruchtkörperform zueinander kaum Übereinstimmungen. Gerronema chrysophyllum besitzt Parallelen im Merkmalsbestand zu Cantharellus-Arten, vor allem zu Arten der Untergattung Phaeocantharellus. Dies kann durch den Aufbau der Huthaut, des verdickenden Hymeniums, der Basidien und der Stieltrama belegt werden. Besonders durch die Ontogenie der Fruchtkörper und der Lamellen wird diese Annahme unterstützt. Haasiella venustissima bleibt trotz neu dargestellter Merkmale der Fruchtkörpermorphologie — wenig differenzierte Huthaut, mehrschichtige Lamellentrama, Kaulozystiden in hymenialer Anordnung — und der Karyologie der Basidie in seiner systematischen Stellung isoliert, zumal Vergleichsdaten anderer, für einen Vergleich notwendiger Arten vielfach fehlen.     

ADRENOCORTICAL TUMORS

Hormonally active tumors of the adrenal cortex are either benign adenomas or adenocarcinomas. They may be located within the adrenal gland or as adrenal rests along the Wolffian tract. Hyperplastic cortical tissue without actual neoplastic formation is also capable of elaborating excessive cortical secretions.At the present state of knowledge, any one or a combination of the following compounds may be elaborated in a given case: the electrolytic, glucogenic, androgenic, or estrogenic corticosteroids.Whether or not Cushing''s syndrome is primarily pituitary or adrenal in origin is still a matter of conjecture.     

Cold exposure and associated metabolic changes in adult tropical beetles exposed to fluctuating thermal regimes

Environmental stress deleteriously affects every aspect of an ectotherm's biological function. Frequent exposure of terrestrial insects to temperature variation has thus led to the evolution of protective biochemical and physiological mechanisms. However, the physiological mechanisms underlying the positive impact of fluctuating thermal regimes (FTRs) on the fitness and survival of cold-exposed insects have not been studied. We have thus investigated the metabolic changes in adults of the beetle Alphitobius diaperinus in order to determine whether FTRs trigger the initiation of a metabolic response involving synthesis of protective compounds, such as free amino acids (FAAs) and polyols. The metabolic profile was analyzed during constant fluctuating thermal regimes (the beetles had daily pulses at higher temperatures that enabled them to recover) and compared with constant cold exposure and untreated controls. The increase of several essential amino acids (Lys, Iso, Leu, Phe and Trp) in cold-exposed beetles supports the conclusion that it results from the breakdown of proteins. Some FAAs have been shown to have cryoprotective properties in insects, but the relationship between FAAs, cold tolerance and survival has not yet been well defined. Instead of considering FAAs only as a part of the osmo- and cryoprotective arsenal, they should also be regarded as main factors involved in the multiple regulatory pathways activated during cold acclimation. Under FTRs, polyol accumulation probably contributes to the increased duration of survival in A. diaperinus.     

Evolutionary transition in symbiotic syndromes enabled diversification of phytophagous insects on an imbalanced diet

Evolutionary adaptations for the exploitation of nutritionally challenging or toxic host plants represent a major force driving the diversification of phytophagous insects. Although symbiotic bacteria are known to have essential nutritional roles for insects, examples of radiations into novel ecological niches following the acquisition of specific symbionts remain scarce. Here we characterized the microbiota across bugs of the family Pyrrhocoridae and investigated whether the acquisition of vitamin-supplementing symbionts enabled the hosts to diversify into the nutritionally imbalanced and chemically well-defended seeds of Malvales plants as a food source. Our results indicate that vitamin-provisioning Actinobacteria (Coriobacterium and Gordonibacter), as well as Firmicutes (Clostridium) and Proteobacteria (Klebsiella) are widespread across Pyrrhocoridae, but absent from the sister family Largidae and other outgroup taxa. Despite the consistent association with a specific microbiota, the Pyrrhocoridae phylogeny is neither congruent with a dendrogram based on the hosts'' microbial community profiles nor phylogenies of individual symbiont strains, indicating frequent horizontal exchange of symbiotic partners. Phylogenetic dating analyses based on the fossil record reveal an origin of the Pyrrhocoridae core microbiota in the late Cretaceous (81.2–86.5 million years ago), following the transition from crypt-associated beta-proteobacterial symbionts to an anaerobic community localized in the M3 region of the midgut. The change in symbiotic syndromes (that is, symbiont identity and localization) and the acquisition of the pyrrhocorid core microbiota followed the evolution of their preferred host plants (Malvales), suggesting that the symbionts facilitated their hosts'' adaptation to this imbalanced nutritional resource and enabled the subsequent diversification in a competition-poor ecological niche.