Mutational variability of enzyme loci in unstable Drosophila melanogaster strains

Biochemical analysis of a number of related unstable Drosophila melanogaster strains was carried out. These strains have been shown to undergo mutational transformations caused by insertion/excision of transposable elements (Gerasimova, 1985). Activity and mobility variants of alpha-GPDH, ADH, SOD, G6PD, 6PGD and EST-6 were analysed. Two loci controlling SOD and 6PGD proved to be invariable, the loci alpha-Gpdh and Est-6 causing reduced activity of their products in the initial strain ctMR2. The direct and reversed transformations analogous to the mutational passages of morphological characters were traced in two loci controlling ADH and G6PD. The data obtained are discussed in terms of up-to-date views on the functional role of transposable elements, in relation to the genetic stability of the strains studied, under the multiple transpositions of mobile elements.     

Molecular-genetic analysis of tandem repeats in intron 6B of the CFTR gene in various populations and in cystic fibrosis patients]

Frequencies of hexa- and heptatandem tetrameric repeats in Russian slavonians from the North-Western part of the country were found to be 0.19 and 0.81, respectively, with the frequency of heterozygotes estimated as 0.31. Similar values of allelic frequencies were found for uzbek and azerbaijan populations (0.24 and 0.76; 0.22 and 0.78, respectively). These data assess the existence of genetic equilibrium of both alleles in the populations studied. Hexa TTR is present twice more often in the CF chromosomes than hepta TTR common for normal chromosomes. Absolute genetic disequilibrium of both TTR alleles was observed for CF chromosomes bearing the F508 mutation. The latter was exclusively detected in a conjunction with hexa TTR allele. Combined application of the F508 test and TTR alleles assay significantly increased the number of totally informative CF-high risk families, and thus might be highly beneficial for a subsequent prenatal diagnosis of CF.     

Dependence of epidermal growth factor activation on its affinity and oligomerization]

Epidermal growth factor receptor (EGF-R) oligomerization has been followed on A-431 cells using covalent labeling by 125I-EGF and EGF-dependent autophosphorylation of receptor-kinase. High molecular weight complexes corresponding to monomeric, dimeric, and trimeric forms of EGF-R are detected. The process of oligomerization occurs effectively at 37 degrees C while at 4 degrees C no oligomer formation is detected. PMA or ATP treatment reduces the number of high-affinity EGF-binding sites but has no influence on dimer formation. Dimerisation of the EGF-R in the absence of the ligand has been established on formalin-fixed A-431 cells.     

The effect of epidermal growth factor on protein phosphorylation in normal and transformed hepatocytes

Qualitative differences in the content of tyrosine-phosphorylated proteins in normal and transformed hepatocytes have been found using the method of two-dimensional electrophoresis. Epidermal growth factor (EGF) has induced quantitative changes in the spectra of phosphotyrosine-containing proteins in normal cells and qualitative changes in the transformed ones. Results of immunoprecipitation with antibodies against phosphotyrosine permit revealing a protein with Mm 50 kDa which is subjected to EGF-dependent tyrosine-phosphorylation in normal hepatocytes. The intensity of protein phosphorylation is 10 times higher in the transformed cells but the dependence of this process on the EGF is not exhibited. The role of protein-tyrosine-kinases in the transmission of a mitogenic signal and in liver carcinogenesis is discussed.