[Acquired radioresistance of progeny of irradiated cells is accompanied by rearrangements in chromatin organization]. / Priobretennaia radiorezistentnost' potomkov obluchennykh kletok soprovozhdaetsia perestroikami v organizatsii khromatina.

gamma-Irradiation action within a dose range of 0-20 Gy on parental djungarian hamster fiborblasts, DH-TK- cell line, and the progenies of these irradiated cells, surviving acute exposure to 20 Gy irradiation, PIC-20 cell line, was examined. The PICs were 3 times more radioresistant than the parental cells as calculated from D0. Using a method of anomalous viscosity time dependence (AVTD) it was revealed that starting (initial) level (in untreated cells) of chromatin compactness in radioresistant progenies was more than 1.4 times as high as for parental cells. The analysis of dose dependence has shown that irradiation with a dose of 5 Gy resulted in complete chromatin loop relaxation in radiosensitive DH-TK- cells and partial one in radioresistant PIC-20 cells. Besides, the beginning of DNA-membrane complexes degradation following the irradiation with doses over 15 Gy in DH-TK- cells was observed. It was shown that the increased state of relative chromatin relaxation in PIC-20 cells determines an increasing in reparation effectiveness that resulted in lower percent of residual damages in these cells. Using the Nosern hybridization method the expression level of mts 1, tag 7 and vseap 1 genes was studied. It is revealed that tag 7 and vseap 1 gene expression in radioresistant cells were correspondingly 6 and 10 times higher than in radiosensitive parental cells and the level of mts 1 gene expression was not changed. So, based on the results obtained we suggest that acquired radioresistance in progenies of irradiated cells is determined by rearrangements in chromatin structure and accompanied constitutive changes of gene expression.

High constitutive level of NF-kappaB is crucial for viability of adenocarcinoma cells.

Most of cells exhibit low nuclear level of NF-kappaB. However, in some cell lines and tissues aberrantly activated NF-kappaB is playing an important role in cell motility, growth control and survival. Here we describe the result of decrease of constitutive NF-kappaB level in different adenocarcinoma cell lines. Treatment of mouse adenocarcinoma cell line CSML-100 with both synthetic (TPCK or PDTC) or natural (I(kappaB)-alpha) NF-kappaB inhibitors caused apoptotic death. Low doses of TPCK were harmless for CSML100 cells but sensitized them to TNF-induced apoptosis. Death of CSML100 cells in the presence of high concentration TPCK was not accompanied with significant changes in c-myc activity but strongly correlated with rapid decrease in p53 level. Thus, mutual behavior p53 and NF-kappaB represented a unique feature of TPCK-induced apoptosis in CSML-100 adenocarcinoma cells.

[KAISO--a new member of the BTB/POZ family specifically bindsto methylated DNA sequences]. / KAISO, novyi chlen VTV/POZ semeistva, spetsifichno sviazyvaetsia s metilirovannymi posledovatel'nostiami DNK.

A protein specifically binding a symmetrically methylated DNA fragment of the first intron of the mts1 gene was studied. The protein was purified by gel filtration and affinity chromatography. Mass spectrometry showed that the protein is Kaiso, a new member of the BTB/POZ family. To study the association with methylated DNA sequences in vivo, the location of Kaiso in NIH 3T3 cells was analyzed. Immunofluorescent staining with polyclonal antibodies against Kaiso showed that the protein is predominantly associated with the nucleoli. The causes of its distribution awaits further investigation. The zinc-finger domains of Kaiso were for the first time demonstrated to specifically recognize symmetrically methylated DNA sequences in vitro.

The p120 catenin partner Kaiso is a DNA methylation-dependent transcriptional repressor.

We describe a novel mammalian DNA binding activity that requires at least two symmetrically methylated CpG dinucleotides in its recognition sequence, preferably within the sequence 5'CGCG. A key component of the activity is Kaiso, a protein with POZ and zinc-finger domains that is known to associate with p120 catenin. We find that Kaiso behaves as a methylation-dependent transcriptional repressor in transient transfection assays. Kaiso is a constituent of one of two methyl-CpG binding complexes originally designated as MeCP1. The data suggest that zinc-finger motifs are responsible for DNA binding, and may therefore target repression to specific methylated regions of the genome. As Kaiso associates with p120 catenin, Kaiso may link events at the cell surface with DNA methylation-dependent gene silencing.

[Genome methylation and its role in functioning of the eukaryotic organism]. / Metilirovanie genoma i ego rol' v funktsionirovanii éukarioticheskogo organizma.

Methylation is a modification that changes the structure and functional status of DNA. Hence it is interesting to study the effect of methylation on basic processes occurring in living cells. In this review, the role of DNA methylation in recombination, replication, transcription regulation, imprinting, tumorigenesis, and tumor progression is considered.

[Functional characteristics of the promoter region of the tag7/PGRP gene in KSML0, KSML100 murine mammary adenocarcinoma cell ines and VMR liver]. / Funktsional'naia kharakteristika promotornoi oblassti gena tag7/PGRP v kletkakh linii KSML0, KSML100 i VMR-pechen' adenokartsinom molochnoi zhelezy myshi.

A study was carried out on the transcription regulation of the tag7/PGRP gene, whose product is similar to cytokines and is involved in recognizing peptidoglycane in mouse mammary adenocarcinoma cell lines KSML0, KSML100, and VMR-liver. The 3250-bp fragment of the promoter region was sequenced and tested for DNase I-hypersensitive sites (DHSs). In the KSML0 cells line, DHSs were found in the vicinity of the TATA box and approximately at position -3000 relative to the transcription start of the gene. Only a DHS cluster near the TATA box was found in the VMR-liver cell line. Regions involved in transcription regulation of the gene in the three cell lines were identified with the use of reporter constructions carrying the CAT gene under the control of deletion derivatives of the tag7/PGRP promoter region. The minimal promoter including only the TATA box with the nearest neighboring sequences was inactive in all cell lines. The elements (enhancers) positively regulating gene transcription in KSML0 and VMR-liver were mapped to region -192, -48. An element accounting for the transcriptional inactivity of the gene in KSML100 cells was assigned to region -315, -3250.

[14 sequences from Chinese hamster genome preferentially binding to the nuclear matrix]. / Identifikatsiya i charakteristiki 14 posledovatel'nostel genoma kitalckogo khomyachka prepochtitel'no svyazyvayushchixcya s yadernym matriksom

Fifteen sequences belonging to the Chinese hamster genome were isolated from a library of sequences preferentially binding to the nuclear matrix (matrix attachment regions, MAR), sequenced, and characterized. Fourteen of the 15 sequences (> 90%) bound to the nuclear matrix with affinities 2.5-60 times higher than those of control DNA fragments containing no MARs. One clone displayed a considerable homology to the ORF1 region of the mouse LINE repeat. Such MARs within LINE repeats may considerably alter the activities of some genes and the transcription status of chromatin domains upon the LINE repeat propagation in the genome over the course of evolution.