[EGF regulation of specific endoribonuclease activity of 26S proteasomes from A431 cells: a potential role of proteasomes in control of mRNA stability].

For the first time it has been shown that RNase activity is induced under the influence of EGF on epidermoid carcinoma cell line A431. Proteasomes from EGF-treated A431 cells destabilize the 3'-untranslated regions of non-muscle beta actin mRNA, creating a specific cleavage pattern. In addition, these particles have been shown to specifically cleave Alu-containing informational RNA.

[Specific regulated endonuclease activity of small RNP, containing prosomes from the A431 cell line: possible mechanisms of regulating the stability of RNA by epidermal growth factor].

A comparative study was made of reactive oxygen species (ROS) in rat embryo fibroblasts and their transformants. Primary rat embryo fibroblasts (REF), REF transformed by the complementing oncogenes E1A plus cHa-ras (cell line E1A + Ras), and REF transformed by E1A plus E1B-19 kDa (cell line E1A + E1B) were studied. ROS generation was measured with microfluorometric assay using fluorescent probe 2',7'-dichlorofluorescin diacetate.

[Prevalence of congenital malformations].

Analyzes the incidence of congenital malformations in children and the relationship between hereditary diseases and average life span for the city of Krasnodar in 1987-1998, with special emphasis on morbidity, death/birth rate, and neonatal mortality caused by hereditary diseases. The incidence of hereditary diseases incompatible with life has increased in recent years and is expected to increase more, due to deterioration of social and economic situation in the country, communal conditions, and ecology.

[Novel endoribonuclease activity of 26S-proteasomes from A-431 cells].

Our analysis detected in 26S proteasomes of human A-431 cells a strong endoribonuclease activity, degrading cytoplasmic high-molecular-mass RNA, particularly, specific mRNAs. Enzymatic nature of this activity has been confirmed, and the optimal conditions studied. This endonuclease activity of proteasomes has not been earlier observed.

[EGF-dependent association of 20S-proteasome and alpha-RNP particles with the epidermal growth factor receptor in A-431 cells].

Here we demonstrate that the epidermal growth factor (EGF) induces association of prosomes (20S-proteasomes) with its receptor in A-431 cells. Additionally, ligand-dependent association of ribonucleoprotein particles (alpha-RNP), containing small ALU-like RNA, with the EGF receptor was demonstrated. A suggestion has been put forward on the involvement of prosomes and alpha-RNP in the EGF signal transmission to different stages of gene expression.

[Change in distribution of actin and intermediate filaments at early stages of action of epidermal growth factor on A431 cells].

By electron microscopy using immunocytochemical reactions on actin and EGF-R with mild glycerinization it became possible to reveal a thick layer of actin filaments under the apical membrane within the first minutes of the impact of EGF on A431 cells. Keratin fibrils being located near the nucleus are transported apart from the membrane. It is supposed that this process is connected with retardation of capping on principles of competition.

[The association of specific RNPs with the EGF receptor in A-431 cells].

One of alpha-RNP proteins (38 kDa alpha-protein) has been revealed as a target of the EGF receptor-associated protein kinase. A specific association of alpha-RNP complexes with the EGF receptor has been demonstrated. The involvement of alpha-RNP in the transduction of the EGF-induced signal has been suggested.

[Chromosome fractionation in a saccharose density gradient for subsequent flow sorting].

The human chromosomes were obtained from lymphoblastoid cell line BOLD with normal karyotype, and separated on the basis of their size by velocity sedimentation at 190 g in sucrose gradient. Different chromosomal fractions were stained by applying fluorochromes with different DNA-base specificity: Hoechst 33258 and Olivomycine and were analysed using dual laser cell-sorter ATC-3000 (Brucker). Velocity sedimentation allowed to enrich certain fractions by individual chromosomes and thus speed up the sorting rate from 90 up to 200 chromosomes per second.

[The epidermal growth factor induces specific changes in the expression of small RNA and of the set of small RNP in A-431 cells].

Specific small ribonucleoprotein (alpha-RNP) complexes have been identified and characterized in the human epidermal carcinoma A-431 cells. The alpha-RNP complexes contain Alu-homologous small RNA, along with other small antisense RNA species. The epidermal growth factor (EGF) has been shown to induce selective specific changes in the expression of the small alpha-RNAs, the expression of the Alu-like RNA being repressed.

Recycling of epidermal growth factor-receptor complexes in A431 cells: identification of dual pathways.

The intracellular sorting of EGF-receptor complexes (EGF-RC) has been studied in human epidermoid carcinoma A431 cells. Recycling of EGF was found to occur rapidly after internalization at 37 degrees C. The initial rate of EGF recycling was reduced at 18 degrees C.

[Cytoskeletal changes in A-431 cells under the action of epidermal growth factor].

By the use of rhodamine-phalloidin, the distribution of actin in A-431 cells during the action of epidermal growth factor (EGF) has been studied. Changes in the pattern of staining are observed in 30-60 s after addition of the EGF. Microvilli and wrinkles are created on the cell surface.

Recycling of epidermal growth factor-receptor complexes in A431 cells.

The fate of epidermal growth factor (EGF) after internalization by human carcinoma A431 cells has been studied. Cells were allowed to internalize 125I-EGF for 10 min at 37 degrees C and treated with acid/salt solution to remove non-internalized ligand. Further incubation of these '125I-EGF-loaded' cells at 37 degrees C results in rapid recycling of internalized 125I-EGF-receptor complexes back to the cell surface.

[The recycling of EGF-receptor complexes in A431 cells].

As was demonstrated elsewhere (L. V. Teslenko et al.

[Changes in the cell surface and cytoskeleton of A-431 cells under the action of epidermal growth factor].

Certain changes in human carcinoma A-431 are found by scanning electron microscopy. The early cell response to growth factor (after 10 minutes) involves a disappearance of microvilli, an appearance of ruffles and rounded cells, along with a decrease in cell attachment to the substrate. The cell surface changes correlate with the state of cytoskeleton elements: the material stained with iron hematoxylin is accumulated in ruffle formation sites.

The endocytosis of epidermal growth factor in A431 cells: a pH of microenvironment and the dynamics of receptor complex dissociation.

The endocytosis and intracellular fate of epidermal growth factor (EGF) were studied in A431 cells. After 15-20 min of internalization at 37 degrees C, rhodamine-labeled EGF (EGF-Rh) accumulated into large juxtanuclear compartment consisting of closely related vesicles. This structure was shown to be localized in the para-Golgi region.

Recycling of epidermal growth factor in A431 cells.

The fate of epidermal growth factor (EGF) after internalization by A431 cells was studied. First, cells containing 125I-EGF-receptor complexes in endosomes were obtained. Subsequent incubation of the cells at 37 degrees C resulted in the recycling of 125I-EGF from endosomes to the cell surface in the receptor-bound state and the gradual release of recycled ligand into the medium.

[A cytoskeletal protein with a molecular weight of 100 kD is a component of the endosomes participating in receptor-mediated endocytosis].

Our previous paper (Rodionov et al., 1985) reported production of monoclonal antibodies RN-17 reacting in cultured fibroblasts with a protein having a molecular weight of 100 kD. Immunofluorescence and immunoelectron microscopy showed that this protein was a component of microtubules, intermediate filaments and coated vesicles.

[Receptor-mediated endocytosis of alpha 2-macroglobulin in living intact 3T3 cells].

Internalization process of the fluoresceinisothiocyanate-labeled alpha 2-macroglobulin (MG-F) in Swiss 3T3 cells has been studied. The presence of internalized MG-F, formation of endocytotic vesicles and endosomal pH value were estimated visually on living monolayer cells with TV microscope, on the base of supervidicon LI-702. The use of the TV method allowed to obtain a series of photographs of cell images without any significant dye fading.

[Effect of the electrochemical sodium gradient on alanine transport in 3T6 and CHO cells].

The dependence of L-alanine uptake by 3T6 and CHO-K1 cells on Na+ electrochemical gradient has been studied. The Na+ chemical gradient was changed by a short-term (partial or complete) replacement of Na+ for choline. The membrane potential change was achieved by addition of potassium ionophore--valinomycin (10 microM) into the medium.