Poly(A) removal is the kinase-regulated step in tumor necrosis factor mRNA decay

Tumor necrosis factor (TNF) is a pleiotropic biomodulator and an important inducer of certain pathophysiologic immune reactions such as granuloma formation, cachexia, and septic shock. The production of TNF by astrocytes, which may figure prominently in the development of immune responses within the central nervous system, is subject to post-transcriptional regulation. We have previously shown that in virus-stimulated astrocytes, inhibition of protein kinase C results in a specific, 10-fold decrease in TNF mRNA half-life. Here we show that the decay of TNF messages induced in the macrophage-like cell line RAW 264.7 by either virus or lipopolysaccharide was subject to similar regulation, and that this pathway influenced the amount of TNF protein released by stimulated cells. Using a modified RNase protection assay, we demonstrate that inhibition of protein kinase C significantly enhanced the rate of poly(A) removal from TNF mRNA, thus facilitating an early event in the process of mRNA degradation.