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The nuclear matrix bound DNA fraction of rat testis showed enrichment in repetitive sequences found in the 450 bp band after gel electrophoresis of the Mspl digested rat DNA. DNA fragments isolated from this band were cloned. DNA of the clone pMspI8 showed homology to some representatives of rat LINE sequence family, and complcxcd in vitro more efficiently with testes nuclear matrix proteins than with yeast ARS1 sequence containing the matrix association region (MAR) or DNA from an other clone, MspI19. Western blot analysis showed that MspI8 sequence interacts with testes matrix protein of about 120 kDa.
The effects of thiamine (vitamin B1) on the level of spontaneous or radia­tion-induced genetic changes in human lymphocytes in vitro were studied. Cul­tured lymphocytes were exposed to increasing concentrations of thiamine (0-500 Ug/ml) and irradiated with X-rays. The DNA damage was estimated as the frequency of micronuclei and apoptotic or necrotic morphological changes in fixed cells. The results show that thiamine alone did not induce genetic changes. A significant decrease in the fraction of apoptotic and necrotic cells was observed in lymphocytes irradiated in the presence of vitamin B1 at concentrations between 1-100 ug/ml compared to those irradiated in the absence of thiamine. Vitamin B1 at 1 and 10 Ug/ml decreased also the extent of radiation-induced formation of micronuclei. Vita­min B1 had no effect on radiation-induced cytotoxicity as measured by nuclear divi­sion index. The results indicate that vitamin B1 protects human cells from radia­tion-induced genetic changes.
A protein which binds specifically to MspI8 (a 454 bp long repeated sequence highly homologous to the 5’ untranslated region (5'UTR) of the LINE 1 sequence) was found and identified in nuclear extracts of rat liver cells. This protein was detected using the electrophoretic mobility shift assay (EMSA) and was purified by Q-Sepharose and DNA affinity chromatography. Its molecular mass was estimated by SDS electrophoresis as 29 kDa. The possibility that this protein (p29) is the rat analogue of human L1PBP-A, specific for the human LINE sequence LPE1, is discussed.
Preincubation of rat liver nuclei with copper ions influenced the stability and protein composition of the nuclear matrices isolated by a "high salt" method. Also the specific interaction between matrix proteins and the kappa Ig matrix attachment region of DNA was affected.
Using the Southwestern blot analysis we have studied the interactions between rat repetitive sequence MspI8 and the nuclear matrix proteins of rat testis cells. Starting from 2 weeks the young to adult animals showed differences in type of testis nuclear matrix proteins recognizing the MspI8 sequence. The same sets of nuclear matrix proteins were detected in some fractions enriched in spermatocytes and spermatides and obtained after fractionation of testis cells of aduit animals by the velocity sedimentation technique.
Eukaryotic chromatin is organized into looped domains formed by attachment of specific DNA sequences (termed MARs or SARs) to network of nuclear proteins (nuclear matrix). We have looked for matrix attachments within 4.9 kb DNA region encompassing rat hsp70.1 gene. Sequences that flank both 3'-end and 5'-end of the gene contain motifs characteristic for MAR/SARs identified in numerous other genes. These flanking sequences formed in vitro complexes with proteins of the nuclear matrix from different rat tissues. Using Southwestern analysis we showed that similar matrix proteins interacted with sequences flanking rat hsp70.1 gene and established MAR from mouse kappa immunoglobulin gene.
In our previous study, a 454 bp DNA fragment was isolated from rat genomic DNA as an element which interacts with nuclear matrix proteins, i.e. a Matrix Associated Region (MAR). Computer analyses revealed that the right half of this fragment, named RME (Rat MAR Element), possesses a high matrix association potential and is likely to be responsible for the matrix association of the whole sequence. RME was used as a probe in an electrophoretic mobility shift assay (EMSA), and with the use of Southwestern blotting, a rat liver nuclear protein which binds specifically to it was identified. Its molecular mass was estimated by SDS-PAGE as 30 kDa (p30). Polyclonal antibodies raised against protein-RME complexes caused a super-shift of specific complexes in EMSA, and bound to p30 in nuclear extracts of rat liver in Western blotting. The immunofluorescence labelling of a rat embryonic fibroblast cell monolayer with anti-p30 antibody revealed a mainly intranuclear pattern of staining.
This study investigates the toxic effect of E(2)nonenal (trans-2-nonenal, T2N) and its conjugate with horse muscle myoglobin (Mb) tested on murine cell line L₉₂₉ and human cell line A₅₄₉, as well as the genotoxic effect of these compounds assayed by measuring of micronuclei in human cells K₅₆₂. It is an aldehyde, which is occurring as the substance responsible for an off flavour in aged beers, but originates also from lipid oxidation in heat processed food. T2N is an aldehyde formed from linoleic acid as a secondary oxidation product. The modification of Mb with T2N was analyzed with the use of SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and electrospray ionization mass spectrometry (ESI-MS). Results from SDS-PAGE suggest that T2N substitutes Mb and additionally causes cross-linking with polymerization of Mb resulting in an insoluble fraction. The ESI-MS spectrum of the soluble fraction used in the toxicity tests, demonstrated that conjugation of T2N with Mb yielded Mb adducts with one residue of trans-2-nonenal per myoglobin molecule as the major fraction and adducts with different numbers of T2N molecules as minor fractions. In the cytotoxicity assay the T2N and its Mb conjugate causes 50 % destruction of cells at the concentration 95-125 pg/ml and 200 pg/ml respectively, when L₉₂₉ and A₅₄₉ cell lines were used, whereas Mb control tested up to 2000 mg/ml was without any cytotoxic effect. In genotoxicity in vitro assay we have observed that the T2N and its Mb conjugate expressed the genotoxicity. The number of micronuclei in human K₅₆₂ cells reac₅₆₂ 26 ± 2.16 promille (MN/1000 cells), comparing to 62 ± 8.64 MN/1000 cells for the reference free T2N, whereas a control value was 10.33 ± 1.25 MN/1000 cells. The studied compounds expressed also the apoptotic effect in K₅₆₂ cells as the number of apoptotic cells increased to 44.67 ±4.92 promille for T2N-Mb, comparing to 168.67 ±37.28 promille for free T2N, whereas a control value was 30.33 ± 1.36 promille for Mb. In these assays the T2N-Mb conjugate is several times more toxic in relation to control protein. Results indicate that T2N adducts with protein are potent to induce various cytotoxic and apoptotic effects when assayed in vitro tests. It suggests that higher level of such aldehyde might create in organism severe potential of toxicity.
 Vitamin D3 (1,25(OH)2D3 (1,25-dihydroxyvitamin D3)) is a hormone playing a crucial role in numerous biological processes in the human body, including induction and control of cell proliferation and differentiation. Numerous data relate the vitamin D3 level with various types of cancer. It has been suggested that SNPs in the vitamin D3 receptor (VDR) gene might influence both the risk of cancer occurrence and cancer progression. The aim of this study was to search for genetic correlations between individual SNPs in the VDR gene and the risk of oral cavity carcinoma. Two SNPs were selected based on the literature and our previous results. Seventy-three patients with squamous cell carcinoma of the head and neck and one hundred control subjects were investigated. Two SNPs in the VDR gene were genotyped in minisequencing reactions followed by capillary electrophoresis. Hardy-Weinberg equilibrium (HWE), the χ2 test and logistic regression were used for statistical analysis. The SNP rs2238135 in the VDR gene displayed statistical differences in frequency between the tested groups (p=0,0007). Furthermore, the G/C genotype of the rs2238135 in the VDR gene was characterized by a 3.16 fold increased risk of oral cavity carcinoma. The obtained results provide evidence for a genetic association between rs2238135 in the VDR gene and the occurrence and risk of oral cavity cancer.
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