Endotoxin induces rat lung ribonuclease activity. We show that within one hour of injection of endotoxin into adult rats, there is an induction of ribonuclease activity in the lung. We suggest that induction by endotoxin of ribonuclease activity is a novel mechanism by which cells could alter gene expression to meet an environmental challenge and caution that the presence of ribonuclease can hinder molecular biological analyses of tissue extracts from endotoxin-treated rats. However, it appears not to be due to known AU binding factors. Preparations of the binding factor also protect interleukin 2 mRNA against degradation by a recently described RNasin-resistant endoribonuclease activity in Jurkat cells.
Protection occurs under the same conditions required to generate the gel-retarded complex.
Single amino acid substitutions at the N-terminus of a recombinant cytotoxic ribonuclease markedly influence biochemical and biological properties. RNasin Ribonuclease Inhibitor Naturally isolated onconase, a cellular RNase with anti-tumor properties, is not inhibited by the placental ribonuclease inhibitor. Recombinant onconase has no activity unless the N-terminal methionine and the glutamate residue is cyclized to form the pyroglutamate moiety. However, conversion of the glutamate to either serine or tyrosine results in RNase activity without processing. This RNase activity is very different from the natural onconase because the Ser and Tyr mutants are inhibited by RNasin Ribonuclease Inhibitor.