Role of p53 in HER2-induced proliferation or apoptosis

HER2 oncogene overexpression has been associated either with proliferation or differentiation and apoptosis. The role of p53 on these different chances was investigated. Wild type (wt) p53-IGROV1 cells showed growth inhibition and apoptosis after HER2 transfection, whereas no anti-proliferative effect was observed in its mutated p53 sub-line unless wt p53 was cotransfected with HER2. Stable HER2 transfectants derived from wt p53 line treated with heregulin-beta1 or epidermal growth factor showed a decrease in proliferation due to a G(2)/M cell cycle block despite normal mitogen-activated protein kinase activation. In these HER2 transfectants, c-Myc and p53 expression were increased, whereas MDM2 was dramatically down-modulated. By contrast, growth factors stimulation of HER2 transfectants with mutated-p53 induced progression through the cell cycle. Together, our data point to a regulatory role for p53 in HER2 signaling.     

Generalization versus Specialization in Pollination Systems: Visitors,Thieves, and Pollinators of Hypoestes aristata (Acanthaceae)

Many recent studies have suggested that the majority of animal-pollinated plants have a higher diversity of pollinators than that expected according to their pollination syndrome. This broad generalization, often based on pollination web data, has been challenged by the fact that some floral visitors recorded in pollination webs are ineffective pollinators. To contribute to this debate, and to obtain a contrast between visitors and pollinators, we studied insect and bird visitors to virgin flowers of Hypoestes aristata in the Bamenda Highlands, Cameroon. We observed the flowers and their visitors for 2-h periods and measured the seed production as a metric of reproductive success. We determined the effects of individual visitors using 2 statistical models, single-visit data that were gathered for more frequent visitor species, and frequency data. This approach enabled us to determine the positive as well as neutral or negative impact of visitors on H. aristata’s reproductive success. We found that (i) this plant is not generalized but rather specialized; although we recorded 15 morphotaxa of visitors, only 3 large bee species seemed to be important pollinators; (ii) the carpenter bee Xylocopa cf. inconstans was both the most frequent and the most effective pollinator; (iii) the honey bee Apis mellifera acted as a nectar thief with apparent negative effects on the plant reproduction; and (iv) the close relationship between H. aristata and carpenter bees was in agreement with the large-bee pollination syndrome of this plant. Our results highlight the need for studies detecting the roles of individual visitors. We showed that such an approach is necessary to evaluate the pollination syndrome hypothesis and create relevant evolutionary and ecological hypotheses.     

Molecular phylogenetic relationships among species of the Malagasy-Comoran gecko genus Paroedura (Squamata: Gekkonidae)

We use approximately 3100bp of mitochondrial (ND2, ND4) and nuclear (RAG1, phosducin) DNA sequence data to recover phylogenetic relationships among 14 of the 16 recognized taxa of the lizard genus Paroedura as well as two undescribed forms. These geckos are endemic to Madagascar and the Comores and are popularly kept and bred by herpetoculturalists. The closest relative of Paroedura is another Indian Ocean leaf-toed gecko, Ebenavia. Both Bayesian inference and maximum parsimony strongly support the monophyly of two major clades within Paroedura that conflict with existing species group assignments based on scale characteristics. Our well-resolved tree elucidates a biogeographic pattern in which eastern Paroedura are most basal and western and south-western species form a monophyletic group. Our data demonstrate the phylogenetic utility of phosducin, a novel marker in squamate phylogenetics, at the intrageneric level.     

Pan‐African phylogeography of a model organism,the African clawed frog ‘Xenopus laevis’

The African clawed frog Xenopus laevis has a large native distribution over much of sub‐Saharan Africa and is a model organism for research, a proposed disease vector, and an invasive species. Despite its prominent role in research and abundance in nature, surprisingly little is known about the phylogeography and evolutionary history of this group. Here, we report an analysis of molecular variation of this clade based on 17 loci (one mitochondrial, 16 nuclear) in up to 159 individuals sampled throughout its native distribution. Phylogenetic relationships among mitochondrial DNA haplotypes were incongruent with those among alleles of the putatively female‐specific sex‐determining gene DM‐W, in contrast to the expectation of strict matrilineal inheritance of both loci. Population structure and evolutionarily diverged lineages were evidenced by analyses of molecular variation in these data. These results further contextualize the chronology, and evolutionary relationships within this group, support the recognition of X. laevis sensu stricto, X. petersii, X. victorianus and herein revalidated X. poweri as separate species. We also propose that portions of the currently recognized distributions of X. laevis (north of the Congo Basin) and X. petersii (south of the Congo Basin) be reassigned to X. poweri.     

Role of Subunits of 60 to 70S Avian Tumor Virus Ribonucleic Acid in Its Template Activity for the Viral Deoxyribonucleic Acid Polymerase

Heating the 60 to 70S ribonucleic acid (RNA) of Rous sarcoma virus (RSV) destroys both its subunit structure and its high template activity for RSV deoxyribonucleic acid (DNA) polymerase. In comparative analyses, it was found that the template activity of the RNA has a thermal transition of 70 C, whereas the 60 to 70S structure dissociates into 30 to 40S and several distinct small subunits with a T(m) of 55 C. Analysis by velocity sedimentation and isopycnic centrifugation of the primary DNA product obtained by incubation of 60 to 70S RSV RNA with RSV DNA polymerase indicated that most, but perhaps not all, DNA was linked to small (<10S) RSV RNA primer. Sixty percent of the high template activity of 60 to 70S RSV RNA lost after heat dissociation could be recovered by incubation of the total RNA under annealing conditions. The template activity of purified 30 to 40S subunits isolated from 60 to 70S RSV RNA was not enhanced significantly by annealing. However, in the presence of small (<10S) subunits also isolated from 60 to 70S RNA, the template activity of 30 to 40S RNA subunits was increased to the same level as that of reannealed total 60 to 70S RNA. It was concluded that neither the 30 to 40S subunits nor most of the 4S subunits of 60 to 70S RSV RNA contribute much as primers to the template activity of 60 to 70S RSV RNA. The predominant primer molecule appears to be a minor component of the <10S subunit fraction of 60 to 70S RSV RNA. Its electrophoretic mobility is similar to, and its dissociation temperature from 60 to 70S RSV RNA is higher than that of the bulk of 60 to 70S RSV RNA-associated 4S RNA. The role of primers in DNA synthesis by RSV DNA polymerase is discussed.     

Neogene sloth assemblages (Mammalia,Pilosa) of the Cocinetas Basin (La Guajira,Colombia): implications for the Great American Biotic Interchange

We describe sloth assemblages from the Cocinetas Basin (La Guajira peninsula, Colombia), found in the Neogene Castilletes and Ware formations, located in northernmost South America, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth, Hyperleptus?, from the early–middle Miocene Castilletes Formation, suggests affinities of this fauna with the distant Santa Cruz Formation and documents a large latitudinal distribution for this taxon. The late Pliocene Ware Formation is much more diverse, with five distinct taxa representing every family of ‘ground sloths’. This diversity is also remarkable at the ecological level, with sloths spanning over two orders of magnitude of body mass and probably having different feeding strategies. Being only a few hundred kilometres away from the Isthmus of Panama, and a few hundred thousand years older than the classically recognized first main pulse of the Great American Biotic interchange (GABI 1), the Ware Formation furthermore documents an important fauna for the understanding of this major event in Neogene palaeobiogeography. The sloths for which unambiguous affinities were recovered are not closely related to the early immigrants found in North America before GABI 1.     

Flow cytometric screening and isolation of Escherichia coli clones which express surface antigens of the oil-degrading microorganism Acinetobacter calcoaceticus RAG-1

Flow cytometry (FCM) in conjunction with immunocytochemical-labeling was used to analyze and screen a population of Escherichia coli clones containing a genomic library from the oil-degrading microorganism Acinetobacter calcoaceticus RAG-1 for the isolation of clones which expressed specific RAG-1 surface antigens. Reconstruction experiments using mixed populations indicated that RAG-1 cells could be clearly distinguished at a ratio of one RAG-1 cell to 500 Escherichia coli cells. Using this technique two clones, WM143 and WM191, were isolated and shown by restriction endonuclease cleavage and Southern hybridization to contain plasmids carrying inserts of RAG-1 DNA of 9.4 and 9.8 kb respectively.Non-common abbreviations FCM flow cytometry - FITC fluorescein-iso-thiocyanate - LB Luria broth - MM minimal salt medium - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride