Role of AUUU sequences in stabilization of granulocyte-macrophage colony-stimulating factor RNA in stimulated cells

RNAs for transiently expressed genes such as oncogenes and cytokines, including granulocyte-monocyte colony-stimulating factor (GM-CSF), have a short half-life (T1/2). A cluster of AUUU sequences identified in the 3′ untranslated (UT) region of these RNAs has been implicated in controlling stability of these transcripts. We examined the role of AUUU sequences in mRNA stability of GM-CSF after stimulation of cells. Human fibroblasts (W138) were stably transfected with chimeric constructs containing the beta-globin gene linked to a 52-bp tail of GM- CSF containing either eight ATTTT (pNEOR beta G-AT) or eight repeats in which the AT sequences have been changed to GC sequences (pNEOR beta G- GC). Data confirmed that AUUU sequences in 3′UT region of GM-CSF play a major role in GM-CSF RNA instability. Stimulators of protein kinase C (PKC), cycloheximide (CHX), sodium fluoride (NaF), and, to a more limited extent, interleukin-1 beta (IL-1 beta), appear to stabilize GM- CSF RNA through these AUUU sequences, but tumor necrosis factor-alpha (TNF-alpha) induces stabilization of GM-CSF RNA through a mechanism independent of their AUUU sequences.