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F Watt

Publications and source records attributed to F Watt.

47 records · Page 3Linked to original sources
PubMed1988

High mobility group proteins 1 and 2 stimulate binding of a specific transcription factor to the adenovirus major late promoter.

High mobility group proteins 1 and 2 (HMGs 1 and 2) are abundant chromosomal proteins which are believed to be preferentially associated with regions of active chromatin. Our previous results have shown that HMGs 1 and 2 can significantly stimulate specific transcription in vitro from the adenovirus major late promoter. This stimulation is now shown to be due, at least in part, to the influence of HMGs 1 and 2 on binding of a specific transcription factor (MLTF) upstream of the start site of the gene to a region (-66 to -51) which is required for optimal transcription both in vivo and in vitro. HMGs 1 and 2 cause both an increase in the rate of binding of the transcription factor to the DNA and alterations to the pattern of the DNaseI footprint of the factor on the DNA. Different binding states of the factor are also observed dependent on the presence of MgCl2, the factor being bound but not protecting the binding region from DNaseI in the absence of MgCl2.

Adenoviridae↗
PubMed1988

Cytosine methylation prevents binding to DNA of a HeLa cell transcription factor required for optimal expression of the adenovirus major late promoter.

Cytosine methylation within CpG dinucleotides has been implicated in the regulation of gene expression in vertebrates and, in some cases, has been shown to be causative in repression of transcription. We have examined whether methylation of CpG dinucleotides located within the binding site for a specific transcription factor, MLTF or USF, affects its binding to DNA. This HeLa cell factor binds to the adenovirus major late promoter (AdMLP), as well as endogenous cellular genes, and stimulates transcription in an in vitro assay. Synthetic oligonucleotides in which 5-methylcytosine replaces cytosine at specific sites were used to generate duplex DNAs, and the formation of complexes of these oligomers with MLTF was studied using a gel retardation assay. Methylation at a CpG site centrally located within the binding site strongly inhibited complex formation, whereas methylation at a site 6 bases away had no demonstrable effect. Methylation at the central site was also shown to inhibit specific transcription in vitro from the AdMLP. Methylation at the central site on only one strand caused a partial inhibition of binding, the effect being greater when the noncoding strand was methylated. The results indicate that in some cases, site-specific methylation may inhibit gene expression directly by blocking binding to DNA of factors required for optimal transcription. Along with other recent findings, they suggest an interplay between DNA methylation and transcription factors in the regulation of gene expression.

Adenoviridae↗
PubMed1988

Element localisation and distribution in the fungi Aureobasidium pullulans and Aspergillus niger, measured using the Oxford scanning proton microprobe.

The distribution and relative concentrations of essential elements were determined in germ tubes of Aureobasidium pullulans and hyphae of Aspergillus niger using the Oxford scanning proton microprobe. In both fungi, K, P and S were the major constituents, with Ca, Na and trace metals like Cu, Mn, Fe and Zn present at lower levels. In A. pullulans, elements were not distributed uniformly throughout the cells and, in general, the highest elemental concentrations occurred at the tip and in the older parts of the germ tube, particularly where there was yeast-like cell or branch development. In A. niger, elemental distribution was more uniform and there was a general gradient of increasing concentration away from the hyphal tip followed by a drop in levels in older regions. The scanning proton microprobe appears to have considerable potential for the investigation of fungal differentiation and morphogenesis.

Aspergillus niger↗
PubMed1985

Hepatic copper distribution in primary biliary cirrhosis shown by the scanning proton microprobe.

A number of conditions are associated with abnormalities of trace metal handling by the liver. We report the application of the Oxford scanning proton microprobe to the analysis of hepatic copper in one such condition, primary biliary cirrhosis. The scanning proton microprobe analyses conventional tissue sections (5-10 micron thickness) and produces simultaneous elemental distribution maps of biologically relevant elements with a spatial resolution of 1 micron and a detection limit better than 1 ppm. We have confirmed the localisation of excess copper to periportal areas and suggest that such accumulation is confined to a proportion of periportal hepatocytes. We have also shown a close spatial correlation between regions of copper accumulation and areas of high sulphur concentration. The copper to sulphur ratio in these areas is consistent with their identity as aggregates of copper loaded metallothionein, and the scanning proton microprobe was further able to show that the aggregates contain less than 30 ppm zinc.

Computers↗
PubMed1984

Z-DNA immunoreactivity of Drosophila polytene chromosomes. Effects of the fixatives 45% acetic acid and 95% ethanol and of DNase I nicking.

Drosophila salivary chromosomes have been isolated at neutral pH and physiological ionic strength. They display only background level binding of antibodies against Z-DNA. Following exposure to the commonly used fixative 45% acetic acid all of the polytene chromosomes, X and autosomes, show a massive increase in anti-Z-DNA antibody binding. The enhancement from background to intense fluorescence occurs whether the chromosomes are stabilised by two orders of magnitude lower concentration of formaldehyde than that used to minimise protein extraction in classical acid squash preparations, or by physiological concentrations of spermine and spermidine. Nicking of acetic acid-treated chromosomes by DNase I dramatically reduces their Z-DNA immunoreactivity. The histones and non-histones extracted by 45% acetic acid from unfixed and formaldehyde-fixed Drosophila chromatin have been analysed. Exposure of isolated salivary chromosomes to the non-protein-extracting fixative 95% ethanol also enhances Z-DNA immunoreactivity. All of these phenomena must be taken into account in the search for the Z-DNA conformation in cells by cytological techniques.

Acetates↗
PubMed1984

Elemental mapping of human nervous tissue using the scanning proton microprobe.

The scanning proton microprobe (SPM) is a powerful multi-elemental analytical instrument capable of elemental mapping at the parts per million level of sensitivity. In this report we demonstrate that the SPM is sufficiently sensitive and versatile to distinguish different regions of the human central nervous system on the basis of differences in their normal endogenous elemental composition.

Brain Mapping↗
PubMed1978

The procuticle of Drosophila: heterogeneity of urea-soluble proteins.

Proteins, soluble in 7 M urea, 4 M guanidine hydrochloride, or 2% sodium dodecyl sulfate, have been extracted from untanned larval cuticles of Drosophila melanogaster. A major protein fraction, apparent molecular weight 8000 - 10 000, is resolved into eight different components (five major, three minor) by gradient gel electrophoresis under nondenaturing conditions. Proteins extracted in 7 M urea have been resolved by diethylaminoethylcellulose chromatography into five fractions, three of which are greatly enriched for electrophoretically homogeneous proteins. The five fractions have different amino acid compositions. Electrophoretic variants involving four of the five major proteins have been obtained. Preliminary genetic analysis indicates that at least three of the five proteins are specified by separate structural genes.

Alleles↗
PubMedDate not supplied

Microanalysis of senile plaques using nuclear microscopy.

Silver-staining "senile" plaques occurring in the brain are a major part of the pathology of Alzheimer's disease. The elemental composition of these structures, and the possible presence of aluminum and silicon in these structures, has been the subject of an increasing research effort over the last decade. However, the results have often been contradictory. Using a scanning proton microprobe, the elemental composition of senile plaques has been determined. This instrument, similar to an electron probe, uses a focused beam of protons scanned across a sample to map the elements. The technique is absolutely quantitative and is sensitive down to the parts per million level. Tissue from six cases of clinically and pathologically characterized cases of Alzheimer's disease and two aged neurologically normal controls was scanned. It was found that aluminum and silicon occur at a level of 50 ppm or greater in the cores of 20% of senile plaques and that the total occurrence of aluminum or silicon in scans containing plaques was not above background. The major uncertainties affecting interpretation of results of this kind are discussed, and it is suggested that the least controllable factor is contamination in the reagents used to prepare and stain the tissue. This indicates that until plaques can be unambiguously identified and analyzed in untreated tissue, no conclusion can be reached on whether senile plaques contain aluminum and silicon.

Aged↗