The relationship between the lipophilicity, cytotoxic effects, and intracellular accumulation for potential antitumor agents, viz., amino complexes of platinum(IV) with the redox-active nitroxyl radicals cis,trans,cis-PtIV(RNH2)(NH3)(OCOR´)2Cl2 (R is 2,2,6,6-tetramethyl-1-oxylpiperidin-4-yl, OCOR´ are n-alkylcarboxylates C2—C8), was studied in comparison with cisplatin. In a series of four platinum nitroxyl complexes (PNCs), an increase in the lipophilicity was found to lead to a considerable increase in the cytotoxicity and the efficiency of accumulation in HeLa cells. However, PNCs are characterized by the slower development of cytotoxic effects after a short time exposure compared with hydrophilic cisplatin. This can be attributed to the fact that PtIV complexes are prodrugs and need to be reduced to chemically more active PtII derivatives in order to exhibit cytotoxic effects.

We synthesized a number of derivatives of 1,2,3-benzotriazole, 1,2,4-triazole, and oxazolidine-2-one derivatives, among which compounds suppressing the growth of the tumor cells HeLa and H1299 were revealed. The studies of the effect of these compounds on the cell cycle and activity of caspase dependent degradation of poly(ADP-ribose) polymerase showed that these compounds at the IC50 doses exhibit cytostatic effect on tumor cells. In the MCF7 cells, these compounds induce an increase in expression of the tumor suppressor p53.

We analyzed the content of lamin B, one of the main proteins of the nuclear membrane, in different chromatin fractions obtained during purification of the nuclear matrix from different cell types. Depending on cell type and nuclear matrix preparation technique, lamin B was found in different not associated with matrix chromatin compartments. This effect was observed after chromatin extraction with ammonium chloride after nucleolysis and after chromatin extraction with sodium chloride before nuclease treatment. These findings suggest that the structure of the nuclear matrix is destabilized in certain extraction procedures and that studies of subcompartmentalization of nuclear macromolecules require additional control of nuclear matrix integrity.

Experiments on resting hepatocytes with inactive c-fos gene and active albumin gene. We revealed that DNA of the transcribed gene is less susceptible to the influence of endogenous Ca2+/Mg2+-dependent DNases in matrix-associated and highly soluble chromatin fractions. In the fraction of low soluble chromatin active gene was more accessible for DNases. Our results indicate that activity of endogenous DNases can change in the transcribed gene locus.

Accumulation of c-fos gene locus DNA In the nuclear matrix of hepatocyte nuclei was observed during induction of c-fos with cycloheximide. No enhanced association with the nuclear matrix was detected for inactive immunoglobulin gene locus. The use of endogenous DNases allows isolation of nuclear matrix preparations enriched with transcribing chromatin.

The degree of nucleolysis is of critical significance for isolation of nuclear matrix (NM) specifically enriched in transcribed DNA sequences, as demonstrated using an example of inactive (c-fos, c-myc, andCκ) and active (p53, albumin, and28S rRNA) genes in resting hepatocytes. The optimal degree of nucleolysis is characterized by degradation of loop domains of chromatin, with the relatively uniform molecular weight distribution of DNA being preserved. Deviation from these parameters leads to nonspecific fragmentation of chromatin in various gene loci and isolation of NM samples nonspecifically enriched with or depleted of transcribed DNA sequences. Under optimal hydrolytic conditions, the transcribed chromatin is more resistant to endogenous DNase attack, which allows selective conservation of its association with the nuclear matrix

In the monolayer of rat hepatocytes in vitro, the circadian rhythms were revealed of 3H-leucine incorporation in proteins and in aminoacyl-tRNA(Leu) fraction. The oscillations were mainly synphasic, though coordination between aminoacylation and protein synthesis was not stable in the coarse of time. In cell free system with the excess of ATP and aa-tRNA, the rhythm of 3H-leucine incorporation was also clear. This means, that oscillatory kinetics of the protein synthesis rate is not caused by oscillation of ATP which has been revealed earlier in the hepatocyte monolayer.