Regulation of the stability of human β interferon mRNA in poly(I)·poly(C)-induced diploid fibroblasts: Anchorage independence of the shutoff mechanism

Abstract

Exposure of diploid human fibroblast (FS-4) monolayer cultures to poly(I)·poly(C) leads to production of β interferons within the first hour, the rate of production peaks approximately 3 hr after induction and is rapidly shut off by 6–8 hr. The rapid shutoff of interferon production is blocked if the induction is carried out in the presence of 5,6-dichloro-1-β- d-ribofuranosylbenzimidazole (DRB, 40 μ M). The rapid and selective inactivation of interferon mRNA that occurs during the shutoff phase in monolayer cultures is anchorage independent and can be preserved in short-term (3–4 hr) suspension cultures prepared from cell monolayers in the shutoff phase. Such inactivation of interferon mRNA is not observed in DRB-containing suspension cultures derived from induced, DRB-treated cell monolayers. Washing of detached, shutoff phase FS-4 cells with buffers lacking Ca 2+ blocks interferon mRNA inactivation while washing these cells with buffers containing 1 m M Ca 2+ preserves the shutoff mechanism. Optimal interferon mRNA turn-over requires both active cellular RNA and protein synthesis and incubation at 37°. These data suggest that the selective inactivation of human fibroblast interferon mRNA during the shutoff phase is an active cellular function which does not require the attachment of cells to a solid substrate.