ADHESION-DEPENDENT REGULATION OF AN A-RICH ELEMENT-BINDING ACTIVITY ASSOCIATED WITH AUF1(U)

Monocyte adherence results in the rapid transcriptional activation and mRNA stabilization of numerous mediators of inflammation and tissue r epair, While the enhancer and promoter elements associated with transc riptional activation have been studied, mechanisms linking adhesion, m RNA stabilization, and translation are unknown. GRO alpha and interleu kin-1 beta (IL-1 beta) mRNAs are highly labile in nonadhered monocytes but stabilize rapidly after adherence, GRO alpha and IL-1 beta transc ripts both contain A+U-rich elements (AREs) in the 3' untranslated reg ion (UTR) which have been directly associated with rapid mRNA turnover . To determine if the GRO alpha ARE region was recognized by fact ors associated dth mRNA degradation, we carried out mobility gel shift ana lyses using a series of RNA probes encompassing the entire GRO alpha t ranscript, Stable complexes were formed only with the proximal 3' UTR which contained the ARE region, The two slower-moving complexes were r apidly depleted following monocyte adherence but not direct integrin e ngagement, Deadherence reactivated the two largest ARE-binding complex es and destabilized IL-1 beta transcripts, Antibody super shift studie s demonstrated that both of these, ARE RNA-binding complexes contained AUF1. The formation of these complexes and the accelerated mRNA turno ver are phosphorylation-dependent events, as both are induced in adher ent monocytes by the tyrosine kinase inhibitor genistein and the p38 M AP kinase inhibitor of IL-1 beta translation, SK&F 86002. These result s demonstrate that cell adhesion and deadhesion rapidly and reversibly modify both cytokine mRNA stability and the RNA-binding complexes ass ociated with AUF1.