Adhesion-Dependent Regulation of an A+U-Rich Element-Binding Activity Associated with AUF1

Abstract

Monocyte adherence results in the rapid transcriptional activation and mRNA stabilization of numerous mediators of inflammation and tissue repair. While the enhancer and promoter elements associated with transcriptional activation have been studied, mechanisms linking adhesion, mRNA stabilization, and translation are unknown. GRO␣ and interleukin-1␤ (IL-1␤) mRNAs are highly labile in nonadhered monocytes but stabilize rapidly after adherence. GRO␣ and IL-1␤ transcripts both contain A؉U-rich elements (AREs) in the 3 untranslated region (UTR) which have been directly associated with rapid mRNA turnover. To determine if the GRO␣ ARE region was recognized by factors associated with mRNA degradation, we carried out mobility gel shift analyses using a series of RNA probes encompassing the entire GRO␣ transcript. Stable complexes were formed only with the proximal 3 UTR which contained the ARE region. The two slower-moving complexes were rapidly depleted following monocyte adherence but not direct integrin engagement. Deadherence reactivated the two largest ARE-binding complexes and destabilized IL-1␤ transcripts. Antibody supershift studies demonstrated that both of these ARE RNA-binding complexes contained AUF1. The formation of these complexes and the accelerated mRNA turnover are phosphorylation-dependent events, as both are induced in adherent monocytes by the tyrosine kinase inhibitor genistein and the p38 MAP kinase inhibitor of IL-1␤ translation, SK&F 86002. These results demonstrate that cell adhesion and deadhesion rapidly and reversibly modify both cytokine mRNA stability and the RNA-binding complexes associated with AUF1.

Prostaglandin E2 Induces the Expression of IL-1α in Colon Cancer Cells

“…Many mRNAs encoding inflammatory gene products are structured for rapid degradation. The 3Ј UTR of the IL-1␣ transcript is AU rich (ARE), and contains at least six copies of the Shaw-Kamens sequence (ATTTA) (28,45). This motif is present in many immediate early genes and is thought to be involved in regulating the rate of mRNA degradation (46).…”

Developmental expression of AUF1 and HuR, two c-myc mRNA binding proteins

“…This could possibly lead to an interchange of mRNA binding proteins, a mechanism which may provide an e cient way of regulating mRNA degradation. In view of experiments performed in vitro (DeMaria and Ma et al, 1996) or with cell cultures (Buzby et al, 1996;Ma et al, 1996;Pende et al, 1996;Sirenko et al, 1997), we could postulate that their binding contributes to mRNA decay. We thus expected to ®nd an inverse relationship between their expression levels and those of c-myc transcripts.…”

Post‐transcriptional regulation of gene expression by degradation of messenger RNAs

“…The affinity of recombinant p37 AUF1 for the ARE motif is closely correlated with its potential to destabilize the mRNA . Inhibition of the p38 pathway stabilizes the AREcontaining mRNAs (Winzen et al, 1999;Lasa et al, 2000), inactivating AUF1 protein (Sirenko et al, 1997), which suggests that p38 is involved in the AUF1 activity. In conclusion, the efficiency of ARE-dependent mRNA turnover is compromised in cells containing low levels of endogenous p37 AUF1 and p40 AUF1 (Ross et al, 1991;Buzby et al, 1996) or following sequestration of AUF1 by treatment with hemin (Loflin et al, 1999).…”