[Metabolism of oligoadenylates in cell nuclei and regulation of protein ADP-ribosylation].

2',5'-Oligo(A)synthetase (2-5A) and 2-phosphodiesterase were found in the L cells nuclei. In the cell nuclei 2-5A is 10-30 times higher, than in the cytoplasm. It is induced by interferon and depends on the cell growth state.

Nerve growth factor induces changes in (2'-5')oligo(A) synthetase and 2'-phosphodiesterase activities during differentiation of PC12 pheochromocytoma cells.

Treatment of rat pheochromocytoma cell line PC12 with Vipera lebetina (snake) nerve growth factor (NGF) induces a rapid increase (from 5 to 25-fold) in the level of (2'-5')oligo(A) synthetase activity and a simultaneous decrease (from 2 to 5-fold) in the activity of 2'-5' A degrading enzymes--2'-phosphodiesterases (2'-PDE). These changes in the enzyme activities led to the significant increase in the intracellular concentration of 2'-5' A. We have found that the serum starvation of PC12 cells causes a 1.

[Regulation of the 2',5'-oligoadenylate level in mouse L cells].

A study of pH dependence for ppp5'A2'p5'A2'p5'A hydrolysis in interferon treated and untreated mouse L-cells extracts led to the detection of two types of the 2'-phosphodiesterase activities: interferon dependent and interferon resistant. Several pH-optima were observed for hydrolysis of ppp5'A2'p5'A2'p5'A in cell extracts after their treatment with non-ionic detergent NP-40 or their differential centrifugation. The 2'-phosphodiesterase activity was found in the membrane fraction as well as in the cytoplasmic one.

Regulation of poly(ADP-ribose) transferase activity by 2',5'-oligoadenylates.

pppA2'pA2'pA appears to be a potent natural noncompetitive inhibitor of poly (ADP-ribose) transferase activity in the histone dependent reaction of ADP-ribosylation with Ki=5 microM. Moreover, it is a noncompetitive inhibitor of the Mg2+ dependent reaction of autoADPRT-ribosylation with Ki=20 microM. The activity of ADPRT falls down abruptly both in the cytoplasm and nuclei of mouse L-cells treated with interferon.