Activation of the murine monocyte/macrophage cell line, J774A1 by poly(A).poly(U): I. Binding of poly(A).poly(U) and induction of oligo-2',5'-adenylate synthetase.

Binding and internalization of the synthetic double-stranded complex poly(A).poly(U) were studied on a murine monocyte/macrophage cell line J774A1. Poly(A).poly(U) increased in a dose-dependent fashion the oligo-2',5'-adenylate synthetase demonstrating that those cells were responsive to this agonist. Binding of [32P]poly(A).[32P]poly(U) to the cells reached an apparent kinetic equilibrium within 4 h and was saturable (apparent Kd = 9.99 +/- 0.09.10(-2) g/l and Bmax 13.3 +/- 5.3.10(-3) g/l per 10(6) cells) and temperature-dependent. The binding of poly(A).poly(U) was competitively inhibited by various polynucleotides but not by other structurally unrelated compounds. Analysis of cell-associated [32P]poly(A).[32P]poly(U) demonstrated a minimal degradation of this polyribonucleotide over a 4-h incubation period. Autoradiography of cells incubated with [3H]poly(A).[3H]poly(U) revealed that poly(A).poly(U) was internalized and migrated to cell nuclei. These results suggest that poly(A).poly(U) is internalized in J774A1 cells via an endocytotic process.