RNA-SYNTHESIS INHIBITION STABILIZES UROKINASE MESSENGER-RNA IN MACROPHAGES

Urokinase-type plasminogen activator (uPA) mRNA is induced in macropha ges by the lineage specific growth factor CSF-1. Upon removal of CSF-1 from bone marrow-derived macrophages (BMM), uPA mRNA decayed with a h alf-life of 2 h. If RNA synthesis inhibitors actinomycin D, 5,6-dichlo ro-1-beta-ribofuranosyl benzimidazole (DRB) or alpha-amanitin were add ed at the time as CSF-1 removal, the uPA mess age was stabilised. This was not a general effect on CSF-1 responsive mRNAs, as c-myc mRNA dec ayed with normal kinetics in the presence of inhibitors. The requireme nt for ongoing RNA synthesis for the degradation of uPA mRNA in BMM su ggests that a component of the degradative pathway may be induced foll owing removal of CSF-1.