Rapid reduction of mRNA coding for 2'-5'-oligoadenylate synthetase in rat pheochromocytoma PC12 cells during apoptosis.

Apoptosis is a form of physiological cell death, characterized by DNA fragmentation, which often depends on RNA and protein synthesis. Because cellular RNA is also degraded during apoptosis we studied the role of the 2'-5'-oligoadenylate (2-5A) synthetase in this process. The product of the synthetase, 2-5A, stimulates endoribonuclease-L-mediated controlled RNA degradation. Here we show that apoptosis is induced in rat phenochromocytoma PC12 cells by tributyltin (TBT) at low concentrations (1 nM); already 5-10 min. after addition of this compound DNA fragmentation resulting in a stepladder-like gel pattern was observed. The level of mRNA coding for 2-5A synthetase was determined using a cloned cDNA from rats. Sequence analyses of the rat 2-5A synthetase (M(r) 40-46,000) revealed high homology to other members of class I synthetase cloned from mouse and human. Applying the rat cDNA as a probe we found that parallel with degradation of DNA the level of mRNA coding for 2-5A synthetase decreased already 7.5 min. after induction of apoptosis by TBT the amount of 2-5A synthetase mRNA was reduced by 60%. This finding indicates that this enzyme is among those mRNAs which are degraded during apoptosis and it suggests that 2-5A synthetase, which is involved in the antiviral response of cells and most likely in the control of cell growth and differentiation, does not play an active role during this process.