Ndently regulate both translation and mRNA instability and that for any given cell type or stage of activation degradation need not be a consequence of translation. Direct evidence for the function of AUF1 in mRNA destabilization might be tough to acquire in monocytes due to the nonproliferative status of those cells. While studies are in progress to assess the THP-1 promonocyte model as an alternative technique that is compatible with transfection approaches, it can be recognized that adhesion initiates a distinctive pattern of tyrosine phosphorylation events in THP-1 cells when compared with the freshly isolated monocytes employed in these research. This consists of each phosphorylation of focal adhesion kinase (FAK), syk, and paxillin which are either absent in monocytes (FAK) or not phosphorylated in human peripheral blood monocytes (29). Our correlative approach supports the hypothesis that AUF1 is responsible, in aspect, for AS-0141 supplier regulation of mRNA decay in monocytes. The results supporting this idea are summarized in Fig. 9. In each and every case, a change in mRNA stability is accompanied by a reciprocal alter in ARE-binding activity. As an example, the rapid and selective alterations of binding exhibited by the lower-mobility complexes (complexes a and b) in response to adherence are accompanied by a fast stabilization of GRO and IL-1 transcripts. In contrast, integrin cross-linking in suspended cells gives equivalent gene induction but fails to stabilize the transcripts or lessen ARE-binding activity (information not shown and reference 30). Deadherence of monocytes which express stable mRNAs for these cytokines benefits in the immediate destabilization in the mRNA accompanied by a restoration in ARE-binding activity (bands a and b). Of particular significance are the effects in the p38 MAP kinase inhibitor (SK F 86002), the MEK inhibitor PD 98059, as well as the tyrosine kinase inhibitor genistein. Exposure to these inhibitors resulted in transcript destabilization and recurrence of ARE mobility shift activity. All of these experiments present robust correlative proof that AUF1 is component in the vital binding complicated regulating destabilization of these cytokines in monocytes. It will likely be critical to establish if the phosphorylation events reflected in these studies indicate that unique elements on the ARE recognition complex are regulated by distinct phosphorylation pathways which influence binding to and/or association with AUF1.We thank Francisco Sanchez-Madrid for the gift of anti- 1 integrin monoclonal antibody TS2/16, Joanna Watson and Chul-Gyu Yoo for assistance in drawing blood, and R. L. Juliano, J. M. Watson, and S. Makarov for their helpful discussions of this work. This investigation was supported by National Institutes of Health grant AI 26774 (J.S.H.), National Institutes of Health instruction grant T32-AI 07401 (C.T.D.), and American Cancer Society grant NP-884 (G.B.).REFERENCES 1. Aghib, D. F., J. M. Bishop, S. Ottolenghi, A. Guerrasio, A. Serra, and G. Saglio. 1990. A 3 truncation of MYC caused by chromosomal translocation in a human T-cell leukemia increases mRNA stability. Oncogene 5:70711. 2. Beekhuizen, H., and R. Van Furth. Monocyte adherence to human vascular endothelium. Behring Inst. Mitt. 92:636. 3. Belasco, J., and G. Brawerman. 1993. Manage of messenger RNA stability. SNCA Protein Data Sheet Academic Press, San Diego, Calif. 4. Bickel, M., Y. Iwai, D. H. Pluznik, and R. B. Cohen. 1992. Binding of sequence-specific proteins towards the adenosine-plus uridine-rich sequences on the muri.
