[ADP-ribosylation intensifies cleavage of DNA loops in the nuclear matrix].

Using DNA pulse field electrophoresis it has been shown that ADP-ribosylation in the nucleoids of human mononuclear leukocytes and rat brain cortex neurons stimulates cleavage of DNA loops at their attachmant sites to the nuclear matrix. The conclusion has been drawn suggesting possible participation of ADP-ribosylation in DNA-topoisomerase II activity modulation in the nuclear matrix of eukaryotic cells.

Participation of Poly(ADP-ribose)-polymerase of nuclear matrix in DNA repair.

The poly(ADP-ribose)-polymerase activity of brain and liver cell nuclei is changed during X-irradiation of rats. In the nuclear matrix, poly(ADP-ribose)-polymerase activity increases at a low dose of irradiation (1.7 Gy) and decreases at a high dose (6.7 Gy). A significant part of the activity of nuclear NMN-adenylyltransferase, a key enzyme for biosynthesis of NAD (the substrate of poly(ADP-ribose)-polymerase), has been found in the nuclear matrix. An interrelation between ADP-ribosylation taking place on the matrix level and eukaryotic cell DNA repair is suggested.

[The effect of the x-ray irradiation of rats on the NAD-pyrophosphorylase and poly(ADP-ribose)polymerase activities of brain nuclei and on the NAD content in nerve tissue]. / Vliianie rentgenovskogo oblucheniia krys na NAD-pirofosforilaznuiu i poli(ADP-riboza)polimeraznuiu aktivnost' iader golovnogo mozga i na soderzhanie NAD v nervnoi tkani.

A study was made of the influence of X-irradiation of rats with various doses on NAD-pyrophosphorylase and poly(ADP-ribose) polymerase activity of brain nuclei. It was shown that X-radiation was ineffective with regard to NAD-pyrophosphorylase activity of nuclei and increased their poly(ADP-ribose) polymerase activity. Stimulation of poly(ADP-ribose) polymerase activity of nuclei was a function of radiation dose and correlated with the decrease in the NAD content of nervous tissue. It was found that mainly nonhistone proteins were ADP-ribosylated in nuclei of both irradiated and nonirradiated rats.

[ADP-ribosylation of nuclear proteins in the rat brain]. / ADP-ribozilirovanie iadernykh belkov golovnogo mozga krys.

The distribution of (ADP-ribose)n synthesized from [14C]NAD labeled at the adenyl ring in several protein fractions of isolated rat brain nuclei was studied. Preferential ADP-ribosylation of nonhistone nuclear proteins was shown to occur. It was demonstrated that pol (ADP-ribose)polymerase and DNA-topoisomerase II are located spatially close to each other. A correlation between ADP-ribosylation and the activity of nuclear matrix DNA-topoisomerase II was established.

Adenosine triphosphatase in the embryonic development of the loach.

The ATPase (ATP-phosphohydrolase) activity of homogenates of eggs of the loach Misgurnus fossilis L. was investigated at various stages of development. Mg-2+- and Ca2- minus 2+-stimulated ATPases are the predominant forms of ATPase activity in the egg, and their level is almost constant during development. The loach egg also contains (Na-+--K-+)-dependent ATPase, which is maximally active at pH 6.85 and at a ratio Na-+:K-+ Equals 5:1. This activity is negligible or absent in homogenates of unfertilized eggs, increases during cleavage, but disappears at the end of the period of cleavage. After this, the (Na-+--K-+)-ATPase activity increases all the way up to the end of the period studied (the gastrula stage)mthe results are discussed in connection with the literature data on changes in ionic homeostasis and other characteristics during early embryogenesis.