Recognition of the CDEI motif GTCACATG by mouse nuclear proteins and interference with the early development of the mouse embryo.

We have reported previously (1) two unexpected consequences of the microinjection into fertilized mouse eggs of a recombinant plasmid designated p12B1, carrying a 343 bp insert of non-repetitive mouse DNA. Injected at very low concentrations, this plasmid could be established as an extrachromosomal genetic element. When injected in greater concentration, an early arrest of embryonic development resulted. In the present work, we have studied this toxic effect in more detail by microinjecting short synthetic oligonucleotides with sequences from the mouse insert. Lethality was associated with the nucleotide sequence GTCACATG, identical with the CDEl element of yeast centromeres. Development of injected embryos was arrested between the one-cell and the early morula stages, with abnormal structures and DNA contents. Electrophoretic mobility shift and DNAse foot-printing assays demonstrated the binding of mouse nuclear protein(s) to the CDEl-like box. Base changes within the CDEl sequence prevented both the toxic effects in embryos and the formation of protein complex in vitro, suggesting that protein binding at such sites in chromosomal DNA plays an important role in early development.     

Organization and expression of a second chromosome follicle cell gene cluster in Drosophila

Four genes expressed during the period of vitelline membrane formation are clustered within 8 kb of DNA in region 26A of the second chromosome. Temporal and quantitative difference in the profiles of accumulated RNA suggest that the genes are independently regulated although they are selectively expressed during the stages of vitelline membrane biosynthesis. In situ hybridization and S1 analyses of RNAs from fractionated eggchambers established that these genes are active only in the follicle cells. S1 mapping with in vitro synthesized RNA probes shows that three of the genes are tandemly oriented. All four appear to be intronless. In vitro translation products from hybrid-selected RNAs indicate that two of these genes code for major vitelline membrane proteins. Sequence analysis of these two genes support this conclusion. The cell- and stage-specific expression of the other two genes, encoding less abundant RNAs, suggests that they also play a role in early eggshell production.     

Germ line transmission of autonomous genetic elements in transgenic mouse strains

Upon microinjection into fertilized mouse eggs of circular molecules of plasmid pPyLT1 carrying the gene encoding the large T protein of polyoma virus within bacterial vector sequences, autonomous circular plasmids were stably maintained in low copy numbers in transgenic strains. These plasmids could be rescued in E. coli by transfection. Integrated forms could be detected neither in somatic tissues, nor in spermatozoa. Efficiency of paternal or maternal transmission was close to 100%. The plasmids had lost or had extensively rearranged the polyoma sequences. In addition, they had acquired defined segments of genomic mouse DNA, which might be responsible for correct segregation of daughter copies at both mitosis and meiosis (centromeric function).     

A murine sequence-specific DNA binding protein shows extensive local similarities to the amyloid precursor protein.

Microinjection experiments suggested previously that protein binding to the DNA nucleotide sequence GTCACATG, identical to the CDEI element of the yeast centromere, plays an important role in the early development of the mouse. We established from a series of overlapping mouse cDNA clones the sequence of a candidate CDEI-binding protein. Synthesis in Escherichia coli of a fusion protein which binds specifically the CDEI box in vitro confirmed its identification. On the other hand, the translated 511 amino acid sequence shows two regions with high degrees of similarity to the protein precursor (APP) of the beta-protein (amyloid) that accumulates in the brain and blood vessels of Alzheimer patients. A continuous stretch of 195 amino acids includes 133 residues identical to part of the extracellular domain of APP, and 48 of the 70 C-terminal residues of the open reading frame are identical to the APP transmembrane and cytoplasmic domains.     

Contribution of the different planktonic microbial assemblages to ETS activity in the Ligurian frontal area: north-west Mediterranean Sea

Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 10⁴ cells ml^–1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 3–10 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect.     

Conditions leading to the establishment of the N (a gene dependent) and A (a gene independent) transformed states after polyoma virus infection of rat fibroblasts.

Infection of normal rat fibroblasts (FR 3T3) with the early tsa mutant of polyoma virus may lead to either the A or the N phenotype, tsa-A transformants, originally derived by agar selection, are not temperature dependent for maintenance of the transformed phenotype, whereas tsa-N transormants revert at high temperature to normal growth control. A transformants did not result from an independent cellular mutation selected in agar medium, but rather from a transformation process distinct from that leading to the N state. It occurred in both liquid and agar media when the infected cells were maintained under growth-restricting conditions, such as absence of anchorage and contact inhibition at confluency. N transformation occurred in cells maintained in active growth after virus infection (sparse cultures on a solid substratum). Physiological conditions during a critical period after virus infection thus appear to be a crucial parameter of the transformation process.     

Nano- and picoplankton growth and production in the Bay of Villefranche sur Mer (N.W. Mediterranean)

Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 m) flagellates but towards the end it was more or less equally divided between the nano- and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nanoor picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.     

Effect of single nucleotide polymorphisms in SEPS1 and SEPP1 on expression in the protein level in metabolic syndrome in subjects with cardiovascular disease

Molecular Biology Reports - Metabolic syndrome (MetS) results from the interaction between environmental and genetic factors. Several previous studies considered the role of selenium in developing...     

Are viruses driving microbial diversification and diversity?

Viruses can influence the genetic diversity of prokaryotes in various ways. They can affect the community composition of prokaryotes by 'killing the winner' and keeping in check competitive dominants. This may sustain species richness and the amount of information encoded in genomes. Viruses can also transfer (viral and host) genes between species. Such mechanisms have probably influenced the speciation of prokaryotes. Whole-genome sequencing has clearly revealed the importance of (virus-mediated) gene transfer. However, its significance for the ecological performance of aquatic microbial communities is only poorly studied, although the few available reports indicate a large potential. Here, we present data supporting the hypothesis that viral genes and viral activity generate genetic variability of prokaryotes and are a driving force for ecological functioning and evolutionary change.